Add Expiring OAuth Access Tokens

What does this MR do?

Fixes #21745 (closed)

Currently our OAuth Applications generate access tokens that have no expiry. Per the issue we will begin generating tokens with a 2 hour expiry for new OAuth applications. Existing application can opt-in via a configuration option. Then in %15.0 we will remove the configuration option and enforce expiry across all applications.

Of note (and we should document this), if a token is generated once and either has an expiry or does not expire, refreshing that token will yield the same result. Refreshing the token does not re-evaluate what the refresh time should be. The token will have to be revoked and re-created to use the new configuration. We will have to decide how to handle this in %15.0 when we remove the configuration and enforce expiry. We can probably do a database migration to force-update all existing tokens to have an expiry of 7200 (2 hours). This should have the same effect as revocation, without the side-effect of actually revoking the token.

documentation will be updated in another MR.

Screenshots or Screencasts (strongly suggested)

Instance-level

Group/User-level

Database

Applications will not be queried by this column so we don't need any indices. We will remove this column in %15.0 via #340848 (closed)

Migrate

== 20210902184334 AddExpireAccessTokensToDoorkeeperApplication: migrating =====
-- add_column(:oauth_applications, :expire_access_tokens, :boolean, {:default=>false, :null=>false})
   -> 0.0093s
== 20210902184334 AddExpireAccessTokensToDoorkeeperApplication: migrated (0.0094s)

Rollback

== 20210902184334 AddExpireAccessTokensToDoorkeeperApplication: reverting =====
-- remove_column(:oauth_applications, :expire_access_tokens, :boolean, {:default=>false, :null=>false})
   -> 0.0084s
== 20210902184334 AddExpireAccessTokensToDoorkeeperApplication: reverted (0.0117s)

How to setup and validate locally (strongly suggested)

Does this MR meet the acceptance criteria?

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