Remove specified labels on issue close

What does this MR do?

Relates to #17461

• Adds boolean field for labels remove_on_issue_close.
• REST and GraphQL API support creating and updating the new value on labels
• Removes labels from issues when they are closed if remove_on_issue_close was true.

Follow up MR will take care of adding the new field to regular rails forms and controllers.

Migration output

Migrate

== 20210507191949 AddRemoveOnIssueCloseToLabels: migrating ====================
-- add_column(:labels, :remove_on_issue_close, :boolean, {:null=>false, :default=>false})
   -> 0.0018s
== 20210507191949 AddRemoveOnIssueCloseToLabels: migrated (0.0075s) ===========

Rollback

== 20210507191949 AddRemoveOnIssueCloseToLabels: reverting ====================
-- remove_column(:labels, :remove_on_issue_close, :boolean)
   -> 0.0013s
== 20210507191949 AddRemoveOnIssueCloseToLabels: reverted (0.0072s) ===========

Query Plans

issue.label_links.with_remove_on_issue_close_labels.delete_all

https://explain.depesz.com/s/yXDU

Cannot run the query on production as the remove_on_issue_close column does not exist yet.

RAW SQL

DELETE
FROM "label_links"
WHERE "label_links"."id" IN
    (SELECT "label_links"."id"
     FROM "label_links"
     INNER JOIN "labels" ON "labels"."id" = "label_links"."label_id"
     WHERE "label_links"."target_type" = 'Issue'
       AND "label_links"."target_id" = 86766093
       AND "labels"."remove_on_issue_close" = TRUE)

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #17461