[ci] Split rubocop setup in rails and non-rails config

Rubocop was not prepared to work with the previous set up and this was
breaking some cops, specially the Rails one.

Splitting the configuration up makes the setup simpler and better to
maintain.

Rubocop todo files were created with:
* rails conf:     rubocop --auto-gen-config --ignore-parent-exclusion
* non-rails conf: rubocop --auto-gen-config

Co-authored-by: Björn Geuken <bgeuken@suse.de>
Co-authored-by: Ana María Martínez Gómez <ammartinez@suse.de>

.rubocop.yml

@@ -1,20 +1,13 @@
-require: rubocop-rspec
-
 inherit_from: .rubocop_todo.yml
 
 AllCops:
   UseCache: true
-  CacheRootDirectory: src/api/tmp/rubocop_cache
+  CacheRootDirectory: tmp/rubocop_cache_root_dir
   MaxFilesInCache: 2000
   Exclude:
-    - 'src/api/tmp/**/*'
-    - 'src/api/lib/templates/**/*'
-    - 'src/api/vendor/bundle/**/*'
+    - 'src/api/**/*'
     - 'docs/api/restility/**/*'
-    - 'src/api/test/fixtures/backend/**/*'
-    - 'src/api/files/*'
     - 'src/backend/**/*'
-    - 'src/api/db/data_schema.rb'
     # These files are RPM spec files
     - 'dist/obs-api-deps.spec'
     - 'dist/obs-server.spec'
@@ -54,16 +47,6 @@ Style/CommandLiteral:
 Style/Documentation:
   Enabled: false
 
-# We need to allow some variables related to rabbiMQ.
-Style/GlobalVars:
-  AllowedVariables: ['$rabbitmq_conn', '$rabbitmq_exchange', '$rabbitmq_channel']
-
-# Checks for chaining of a block after another block that spans multiple lines.
-# We disabled this cop because of Rantly.
-Style/MultilineBlockChain:
-  Exclude:
-    - 'src/api/spec/**/*'
-
 # Checks for redundant `return` expressions
 Style/RedundantReturn:
   Enabled: false
@@ -76,10 +59,6 @@ Style/WordArray:
 
 ##################### Metrics ##################################
 
-Metrics/BlockLength:
-  Exclude:
-    - 'src/api/config/routes.rb'
-
 # Checks if the length a class exceeds some maximum value
 Metrics/ClassLength:
   Severity: refactor
@@ -92,41 +71,3 @@ Metrics/LineLength:
 # Checks if the length a module exceeds some maximum value
 Metrics/ModuleLength:
   Severity: refactor
-
-##################### Rails ##################################
-
-Rails:
-  Enabled: true
-
-# Actually is not possible to enable this cop because we have several overwritten methods.
-Rails/DynamicFindBy:
-  Enabled: false
-
-# Enforces that 'exit' calls are not used.
-Rails/Exit:
-  Exclude:
-    - 'src/api/lib/memory_dumper.rb'
-
-Rails/HasAndBelongsToMany:
-  Enabled: false
-
-# FIXME: Disabled due to a bug in Rubocop. Once it is fixed in this PR (https://github.com/bbatsov/rubocop/pull/5707), it could be enabled again
-Rails/HttpStatus:
-  Enabled: false
-
-# Checks for the use of output calls like puts and print
-Rails/Output:
-  Exclude:
-    - 'src/api/app/jobs/*'
-    - 'src/api/config/*'
-    - 'src/api/db/**/*'
-    - 'src/api/lib/**/*'
-
-# Disabled due to a bug
-Rails/BulkChangeTable:
-  Enabled: false
-
-# Disabled as we currently violate it everywhere in spec/features directory
-# we first need to discuss if we want to move this directory and then fix the violation
-Capybara/FeatureMethods:
-  Enabled: false