Enables frozen string for the following:

* app/controllers/dashboard/**/*.rb
* app/controllers/explore/**/*.rb
* app/controllers/google_api/**/*.rb
* app/controllers/groups/**/*.rb
* app/controllers/import/**/*.rb
* app/controllers/instance_statistics/**/*.rb
* app/controllers/ldap/**/*.rb
* app/controllers/oauth/**/*.rb
* app/controllers/profiles/**/*.rb

Partially addresses #47424.

This whitelists all existing offenses for the various CodeReuse cops, of
which most are triggered by the CodeReuse/ActiveRecord cop.

There's no need to add a redundant message to the errors if the
model is invalid. This cleans up the message as well for the importer.

Importing a project from GitHub for a project namespace that already exists
would show an unhelpful error, "An error occurred while importing project."
We now add the base message from Projects::CreateService when this fails.

Closes #47365

James Lopez authored 7 years ago and Robert Speicher committed 7 years ago

[10.4] Fix GH namespace security issue