feat(cloudfront): Initial CloudFront redesign (aws#8982)

See aws/aws-cdk-rfcs#174 for the design that inspired this implementation.

The goal of this initial PR is to get the new Distribution construct to the point where it supports the most common use cases, in terms of single- and multi-origin and behaviors with the most common properties exposed and working. This is not intended to be a complete/exhaustive implementation, but does allow for users with S3 buckets to create CloudFront distributions more easily than the existing construct today.

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-cloudfront/README.md

@@ -1,18 +1,137 @@
 ## Amazon CloudFront Construct Library
+
 <!--BEGIN STABILITY BANNER-->
 ---
 
-![cfn-resources: Stable](https://img.shields.io/badge/cfn--resources-stable-success.svg?style=for-the-badge)
+| Features | Stability |
+| --- | --- |
+| CFN Resources | ![Stable](https://img.shields.io/badge/stable-success.svg?style=for-the-badge) |
+| Higher level constructs for Distribution | ![Experimental](https://img.shields.io/badge/experimental-important.svg?style=for-the-badge) |
+| Higher level constructs for CloudFrontWebDistribution | ![Stable](https://img.shields.io/badge/stable-success.svg?style=for-the-badge) |
 
-> All classes with the `Cfn` prefix in this module ([CFN Resources](https://docs.aws.amazon.com/cdk/latest/guide/constructs.html#constructs_lib)) are always stable and safe to use.
+> **CFN Resources:** All classes with the `Cfn` prefix in this module ([CFN Resources](https://docs.aws.amazon.com/cdk/latest/guide/constructs.html#constructs_lib)) are always stable and safe to use.
 
-![cdk-constructs: Experimental](https://img.shields.io/badge/cdk--constructs-experimental-important.svg?style=for-the-badge)
+> **Experimental:** Higher level constructs in this module that are marked as experimental are under active development. They are subject to non-backward compatible changes or removal in any future version. These are not subject to the [Semantic Versioning](https://semver.org/) model and breaking changes will be announced in the release notes. This means that while you may use them, you may need to update your source code when upgrading to a newer version of this package.
 
-> The APIs of higher level constructs in this module are experimental and under active development. They are subject to non-backward compatible changes or removal in any future version. These are not subject to the [Semantic Versioning](https://semver.org/) model and breaking changes will be announced in the release notes. This means that while you may use them, you may need to update your source code when upgrading to a newer version of this package.
+> **Stable:** Higher level constructs in this module that are marked stable will not undergo any breaking changes. They will strictly follow the [Semantic Versioning](https://semver.org/) model.
 
 ---
 <!--END STABILITY BANNER-->
 
+Amazon CloudFront is a web service that speeds up distribution of your static and dynamic web content, such as .html, .css, .js, and image files, to
+your users. CloudFront delivers your content through a worldwide network of data centers called edge locations. When a user requests content that
+you're serving with CloudFront, the user is routed to the edge location that provides the lowest latency, so that content is delivered with the best
+possible performance.
+
+## Distribution API - Experimental
+
+![cdk-constructs: Experimental](https://img.shields.io/badge/cdk--constructs-experimental-important.svg?style=for-the-badge)
+
+The `Distribution` API is currently being built to replace the existing `CloudFrontWebDistribution` API. The `Distribution` API is optimized for the
+most common use cases of CloudFront distributions (e.g., single origin and behavior, few customizations) while still providing the ability for more
+advanced use cases. The API focuses on simplicity for the common use cases, and convenience methods for creating the behaviors and origins necessary
+for more complex use cases.
+
+### Creating a distribution
+
+CloudFront distributions deliver your content from one or more origins; an origin is the location where you store the original version of your
+content. Origins can be created from S3 buckets or a custom origin (HTTP server). Each distribution has a default behavior which applies to all
+requests to that distribution, and routes requests to a primary origin.
+
+#### From an S3 Bucket
+
+An S3 bucket can be added as an origin. If the bucket is configured as a website endpoint, the distribution can use S3 redirects and S3 custom error
+documents.
+
+```ts
+import * as cloudfront from '@aws-cdk/aws-cloudfront';
+
+// Creates a distribution for a S3 bucket.
+const myBucket = new s3.Bucket(this, 'myBucket');
+new cloudfront.Distribution(this, 'myDist', {
+  defaultBehavior: { origin: cloudfront.Origin.fromBucket(myBucket) },
+});
+```
+
+The above will treat the bucket differently based on if `IBucket.isWebsite` is set or not. If the bucket is configured as a website, the bucket is
+treated as an HTTP origin, and the built-in S3 redirects and error pages can be used. Otherwise, the bucket is handled as a bucket origin and
+CloudFront's redirect and error handling will be used. In the latter case, the Origin wil create an origin access identity and grant it access to the
+underlying bucket. This can be used in conjunction with a bucket that is not public to require that your users access your content using CloudFront
+URLs and not S3 URLs directly.
+
+### Domain Names and Certificates
+
+When you create a distribution, CloudFront assigns a domain name for the distribution, for example: `d111111abcdef8.cloudfront.net`; this value can
+be retrieved from `distribution.distributionDomainName`. CloudFront distributions use a default certificate (`*.cloudfront.net`) to support HTTPS by
+default. If you want to use your own domain name, such as `www.example.com`, you must associate a certificate with your distribution that contains
+your domain name. The certificate must be present in the AWS Certificate Manager (ACM) service in the US East (N. Virginia) region; the certificate
+may either be created by ACM, or created elsewhere and imported into ACM.
+
+```ts
+const myCertificate = new acm.DnsValidatedCertificate(this, 'mySiteCert', {
+  domainName: 'www.example.com',
+  hostedZone,
+});
+new cloudfront.Distribution(this, 'myDist', {
+  defaultBehavior: { origin: cloudfront.Origin.fromBucket(myBucket) },
+  certificate: myCertificate,
+});
+```
+
+### Multiple Behaviors & Origins
+
+Each distribution has a default behavior which applies to all requests to that distribution; additional behaviors may be specified for a
+given URL path pattern. Behaviors allow routing with multiple origins, controlling which HTTP methods to support, whether to require users to
+use HTTPS, and what query strings or cookies to forward to your origin, among others.
+
+The properties of the default behavior can be adjusted as part of the distribution creation. The following example shows configuring the HTTP
+methods and viewer protocol policy of the cache.
+
+```ts
+const myWebDistribution = new cloudfront.Distribution(this, 'myDist', {
+  defaultBehavior: {
+    origin: cloudfront.Origin.fromBucket(myBucket),
+    allowedMethods: AllowedMethods.ALLOW_ALL,
+    viewerProtocolPolicy: ViewerProtocolPolicy.REDIRECT_TO_HTTPS,
+  }
+});
+```
+
+Additional behaviors can be specified at creation, or added after the initial creation. Each additional behavior is associated with an origin,
+and enable customization for a specific set of resources based on a URL path pattern. For example, we can add a behavior to `myWebDistribution` to
+override the default time-to-live (TTL) for all of the images.
+
+```ts
+myWebDistribution.addBehavior('/images/*.jpg', cloudfront.Origin.fromBucket(myOtherBucket), {
+  viewerProtocolPolicy: ViewerProtocolPolicy.REDIRECT_TO_HTTPS,
+  defaultTtl: cdk.Duration.days(7),
+});
+```
+
+These behaviors can also be specified at distribution creation time.
+
+```ts
+const bucketOrigin = cloudfront.Origin.fromBucket(myBucket);
+new cloudfront.Distribution(this, 'myDist', {
+  defaultBehavior: {
+    origin: bucketOrigin,
+    allowedMethods: AllowedMethods.ALLOW_ALL,
+    viewerProtocolPolicy: ViewerProtocolPolicy.REDIRECT_TO_HTTPS,
+  },
+  additionalBehaviors: {
+    '/images/*.jpg': {
+      origin: bucketOrigin,
+      viewerProtocolPolicy: ViewerProtocolPolicy.REDIRECT_TO_HTTPS,
+      defaultTtl: cdk.Duration.days(7),
+    },
+  },
+});
+```
+
+## CloudFrontWebDistribution API - Stable
+
+![cdk-constructs: Stable](https://img.shields.io/badge/cdk--constructs-stable-success.svg?style=for-the-badge)
+
 A CloudFront construct - for setting up the AWS CDN with ease!
 
 Example usage:
@@ -75,14 +194,15 @@ CloudFront supports adding restrictions to your distribution.
 See [Restricting the Geographic Distribution of Your Content](https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/georestrictions.html) in the CloudFront User Guide.
 
 Example:
+
 ```ts
 new cloudfront.CloudFrontWebDistribution(stack, 'MyDistribution', {
    //...
     geoRestriction: GeoRestriction.whitelist('US', 'UK')
 });
 ```
 
-### Connection behaviors between CloudFront and your origin.
+### Connection behaviors between CloudFront and your origin
 
 CloudFront provides you even more control over the connection behaviors between CloudFront and your origin. You can now configure the number of connection attempts CloudFront will make to your origin and the origin connection timeout for each attempt.