feat(transactions): Add transaction_info.source [INGEST-1427]

src/docs/sdk/event-payloads/properties/transaction_info.mdx

@@ -0,0 +1,27 @@
+`transaction_info`
+
+: _Recommended_. Additional information about the name of the transaction.
+
+```json
+{
+  "transaction_info": {
+    "source": "url"
+  }
+}
+```
+
+`transaction_info.source`
+
+: _Recommended_. Contains information about how the name of the transaction was determined.
+This will be used by the server to decide whether or not to scrub identifiers
+from the transaction name, or replace the entire name with a placeholder.
+
+| Source              | Description                                                                                                                     | <div style="width:220px">Examples</div>                |
+| ------------------- | ------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------ |
+| `custom`            | User-defined name, see [`setTransactionName()`](https://docs.sentry.io/platforms/javascript/enriching-events/transaction-name/) | `my_transaction`                                       |
+| `url`               | Raw URL, potentially containing identifiers.                                                                                    | `/auth/login/john123/`<br />`GET /auth/login/john123/` |
+| `route`             | Parametrized URL / route                                                                                                        | `/auth/login/:userId/`<br />`GET /auth/login/{user}/`  |
+| `view`              | Name of the view handling the request.                                                                                          | `UserListView`                                         |
+| `component`         | Named after a software component, such as a function or class name.                                                             | `AuthLogin.login`<br /> `LoginActivity.login_button`   |
+| `task`              | Name of a background task (e.g. a Celery task)                                                                                  | `sentry.tasks.do_something`                            |
+| `unknown` (default) | This is the default value set by Relay for legacy SDKs.                                                                         |                                                        |

src/docs/sdk/event-payloads/transaction.mdx

@@ -63,3 +63,7 @@ import "./properties/status.mdx";
 import "./properties/spans.mdx";
 
 import "./properties/measurements.mdx";
+
+## Transaction Annotations
+
+import "./properties/transaction_info.mdx";

src/docs/sdk/performance/index.mdx

@@ -2,7 +2,7 @@
 title: "Guidelines for Performance Monitoring"
 ---
 
-This document covers how SDKs should add support for Performance Monitoring  with [Distributed
+This document covers how SDKs should add support for Performance Monitoring with [Distributed
 Tracing](https://docs.sentry.io/product/performance/distributed-tracing/).
 
 This should give an overview of the APIs that SDKs need to implement, without
@@ -64,6 +64,7 @@ The [Transaction](/sdk/event-payloads/transaction/) class is like a span, with a
 few key differences:
 
 - Transactions have `name`, spans don't.
+- Transactions must specify the [source](/sdk/event-payloads/transaction/#transaction-annotations) of its `name` to indicate how the transaction name was generated.
 - Calling the `finish` method on spans record the span's end timestamp. For
   transactions, the `finish` method additionally sends an event to Sentry.
 
@@ -90,7 +91,6 @@ tree as well as the unit of reporting to Sentry.
   - `TransactionContext` should have a static/ctor method called `fromSentryTrace` which prefills a `TransactionContext` with data received from a `sentry-trace` header value
   - `TransactionContext` should have a static/ctor method called `continueFromHeaders(headerMap)` which is really just a thin wrapper around `fromSentryTrace(headerMap.get("sentry-trace"))` right now. This should be preferred by integration/framework-sdk authors over `fromSentryTrace` as it hides the exact header names used deeper in the core sdk, and leaves opportunity for using additional headers (from the W3C) in the future without changing all integrations.
 
-
 - `Span.finish()`
 
   - Accepts an optional `endTimestamp` to allow users to set a custom `endTimestamp` on the finished span
@@ -196,6 +196,7 @@ keep track of it themselves.
   - The value should be the trace header string of the `Span` that is currently on the `Scope`
 
 - Introduce a method called `startTransaction`
+
   - Takes the same two arguments as `Sentry.startTransaction`
   - Creates a new `Transaction` instance
   - Should implement sampling as described in more detail in the 'Sampling' section of this document