Add endpoint attribute to cognito_user_pool

[bespokebob]

Cognito User Pools have a provider/issuer/endpoint name (I can't find a consistent name for this) of the format cognito-idp..amazonaws.com/<YOUR_USER_POOL_ID>. This name is used by various clients (as the token issuer, and to form the URL to retrieve the JWKs), and for configuring the user pool as an identity provider in a Cognito Identity Pool.

Fixes #4700

Changes proposed in this pull request:

• Adds endpoint attribute to cognito_user_pool

Output from acceptance testing:

$ make testacc TEST=./aws TESTARGS='-run=TestAccAWSCognitoUserPool_basic'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./aws -v -run=TestAccAWSCognitoUserPool_basic -timeout 120m
=== RUN   TestAccAWSCognitoUserPool_basic
--- PASS: TestAccAWSCognitoUserPool_basic (14.82s)
PASS
ok  	github.com/terraform-providers/terraform-provider-aws/aws	25.618s

[bflad]

Thanks for this contribution! LGTM with one minor documentation nitpick, which I'll address post-merge. 🚀

15 tests passed (all tests)
=== RUN   TestAccAWSCognitoUserPool_basic
--- PASS: TestAccAWSCognitoUserPool_basic (8.60s)
=== RUN   TestAccAWSCognitoUserPool_importBasic
--- PASS: TestAccAWSCognitoUserPool_importBasic (9.62s)
=== RUN   TestAccAWSCognitoUserPool_withTags
--- PASS: TestAccAWSCognitoUserPool_withTags (13.64s)
=== RUN   TestAccAWSCognitoUserPool_withSmsVerificationMessage
--- PASS: TestAccAWSCognitoUserPool_withSmsVerificationMessage (14.30s)
=== RUN   TestAccAWSCognitoUserPool_withAdminCreateUserConfiguration
--- PASS: TestAccAWSCognitoUserPool_withAdminCreateUserConfiguration (14.44s)
=== RUN   TestAccAWSCognitoUserPool_withDeviceConfiguration
--- PASS: TestAccAWSCognitoUserPool_withDeviceConfiguration (14.97s)
=== RUN   TestAccAWSCognitoUserPool_withAliasAttributes
--- PASS: TestAccAWSCognitoUserPool_withAliasAttributes (20.58s)
=== RUN   TestAccAWSCognitoUserPool_withEmailConfiguration
--- PASS: TestAccAWSCognitoUserPool_withEmailConfiguration (23.20s)
=== RUN   TestAccAWSCognitoUserPool_withSchemaAttributes
--- PASS: TestAccAWSCognitoUserPool_withSchemaAttributes (24.37s)
=== RUN   TestAccAWSCognitoUserPool_withSmsConfiguration
--- PASS: TestAccAWSCognitoUserPool_withSmsConfiguration (26.11s)
=== RUN   TestAccAWSCognitoUserPool_withLambdaConfig
--- PASS: TestAccAWSCognitoUserPool_withLambdaConfig (32.79s)
=== RUN   TestAccAWSCognitoUserPool_withSmsConfigurationUpdated
--- PASS: TestAccAWSCognitoUserPool_withSmsConfigurationUpdated (36.27s)
=== RUN   TestAccAWSCognitoUserPool_withVerificationMessageTemplate
--- PASS: TestAccAWSCognitoUserPool_withVerificationMessageTemplate (37.22s)
=== RUN   TestAccAWSCognitoUserPool_withPasswordPolicy
--- PASS: TestAccAWSCognitoUserPool_withPasswordPolicy (38.04s)
=== RUN   TestAccAWSCognitoUserPool_withEmailVerificationMessage
--- PASS: TestAccAWSCognitoUserPool_withEmailVerificationMessage (41.57s)

[bflad]

Since the Cognito documentation does not signify what this attribute's value might be we should include an example of what is meant here, e.g. Example: cognito-idp.us-east-1.amazonaws.com/xxxx_yyyyy

[bflad]

This has been released in version 1.22.0 of the AWS provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!