[#1682] Fixed Basic Auth permissions issue by disabling OAuth scopes checks when password is provided. Refactored plugs skipping functionality.

[#2349] Made :skip_plug/2 prevent plug from being executed even if explicitly called. Refactoring. Tests.

Enforcement of OAuth scopes check for authenticated API endpoints, :skip_plug plug to mark a plug explicitly skipped (disabled).

This reverts commit 1ad71592.

Since it had no limit on the number on concurrent processes it OOM killed
instances while rendering hellthreads. When I tried introducing a
concurrency limit with Task.async_stream/manual folds it lead to about 3 times
worse performance on threads larger than 1000 activities (we are talking
30s vs 1.2 minutes), I think this is not worth the about 1.5 times
performance increase on smaller threads when using it.

OAuthController#create_authorization user retrieval / creation, errors handling, template & layout selection.

this avoids complete timeline breakage when an activity fucks up
rendering.