Add health check for SendGrid

[manne]

What this PR does / why we need it:
Adds an health check for SendGrid

Which issue(s) this PR fixes:
none

Special notes for your reviewer:
The health check utilizes the sandbox mode with a valid email.
The email is actually not sent to the recipient. The email request is sent to a SendGrid server, there the email is being validated.

An excerpt from the linked sandbox documentation.

Sandbox mode is an optional parameter within mail_settings. Enabling sandbox mode allows you to send a test email to ensure that your request body is formatted correctly without delivering the email to any of your recipients.
When making a request with sandbox mode enabled, we will validate the form, type, and shape of your request. In other words, sandbox mode will validate each parameter you include and the structure of your JSON payload. [...]

The validation also implies that the API key is correct and email can generally being delivered (e.g there is at least one sender identity). And of course SendGrid services are available.

Does this PR introduce a user-facing change?:
no

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Unit tests passing
• End-to-end tests passing
  • not all on my machine.
• Extended the documentation
  • I could not find a place where to add the documentation. The unit tests should be sufficient ;)
• Provided sample for the feature
  • There are two unit tests

[unaizorrilla]

Let me a couple of days to review this!

Thanks for contribute this

[unaizorrilla]

Hi @manne

Looks good, can you address the feedback?

[unaizorrilla]

we use name ?? NAME instead creating registrationName variable on the others healthchecks

[manne]

Sorry @unaizorrilla I do not understand you.

variable on the others healthchecks

do you mean?

return builder.Add(new HealthCheckRegistration(
                name ?? NAME,

Then I have to do this builder.Services.AddHttpClient(name ?? NAME);. Or do this builder.Services.AddHttpClient();?

Or did I miss something else? Did not understand the

[unaizorrilla]

yeap, don't see this variable is used on both places! is ok!

[unaizorrilla]

I know others healthcheck's like ( uris ) using this pattern, but probably inject Ihttpclientfactory is more natural here!!

[manne]

How should I invoke _httpClientFactory.CreateClient()
A. with a name or
B. without a name

If A. which value?
I) The name of the healthcheck passed in with AddSendGrid(...)
II) A name specific for the SendGridHealthCheck class (as in

AspNetCore.Diagnostics.HealthChecks/src/HealthChecks.UI/Core/Notifications/WebHookFailureNotifier.cs

Line 35 in 19bb7ed

_httpClient = httpClientFactory.CreateClient(Keys.HEALTH_CHECK_WEBHOOK_HTTP_CLIENT_NAME);

)

[unaizorrilla]

is more natural, if ( response.IsSuccessStatusCode ) instead this comparasion

[unaizorrilla]

Can you reduce if/else

if (!response.IsSuccessStatusCode)
{
return new HealthCheckResult( ..... )
}
return HealthCheckResult.Healty()

[manne]

Unfortunately this can not be done, because await client.SendEmailAsync(msg, cancellationToken) returns the type Task<Response> and Response is a SendGrip C# specific type.

Also the SendGrid documentation explicitly states that a 200 is returned.
Whereas IsSuccessStatusCode is

        public bool IsSuccessStatusCode
        {
            get { return ((int)_statusCode >= 200) && ((int)_statusCode <= 299); }
        }

Reference dotnet/runtime

[unaizorrilla]

IsSuccessStatusCode include 200 and all 200-299 are Success response, I think is more natural!

[unaizorrilla]

I will merge this weekend! Looks good !

[unaizorrilla]

Merged with minor changes on healthcheck!! When release build finished a new package 3.1.1-preview1 will be available for sendgrid.

If package is working fine we can move version to release!