Remove rails observers from application

Gemfile

Gemfile.lock

app/models/users_project.rb

app/observers/base_observer.rb

app/observers/users_project_observer.rb

config/application.rb

spec/features/admin/admin_users_spec.rb

spec/features/profile_spec.rb

spec/features/projects_spec.rb

spec/features/search_spec.rb

spec/models/project_spec.rb

spec/models/system_hook_spec.rb

spec/models/user_spec.rb

spec/observers/users_project_observer_spec.rb

spec/requests/api/branches_spec.rb

spec/requests/api/commits_spec.rb

spec/requests/api/files_spec.rb

spec/requests/api/internal_spec.rb

spec/requests/api/issues_spec.rb

spec/requests/api/merge_requests_spec.rb