Since trust will break if Quay makes changes, disable all Quay tag-change APIs and build APIs+webhooks when trust is enabled on a repository. Once we get Quay signing things itself, we can revisit this.
* Add flag to enable trust per repo
* Add api for enabling/disabling trust
* Add new LogEntryKind for changing repo trust settings
Also add tests for repo trust api
* Add `set_trust` method to repository
* Expose new logkind to UI
* Fix registry tests
* Rebase migrations and regen test.db
* Raise downstreamissue if trust metadata can't be removed
* Refactor change_repo_trust
* Add show_if to change_repo_trust endpoint
This feature is subtle but very important: Currently, when a user logs in via an "external" auth system (such as Github), they are either logged into an existing bound account or a new account is created for them in the database. While this normally works jut fine, it hits a roadblock when the *internal* auth system configured is not the database, but instead something like LDAP. In that case, *most* Enterprise customers will prefer that logging in via external auth (like OIDC) will also *automatically* bind the newly created account to the backing *internal* auth account. For example, login via PingFederate OIDC (backed by LDAP) should also bind the new QE account to the associated LDAP account, via either username or email. This change allows for this binding field to be specified, and thereafter will perform the proper lookups and bindings.
