Refactor: Simplify mime_types_for implementation (#2639)

Replace each_with_object with invert.transform_keys! for a more
idiomatic Ruby implementation. This also adds a performance
optimization by only splitting strings that contain ';' instead
of always splitting.

Co-authored-by: Daniel (dB.) Doubrovkine <[email protected]>

Author: ericproulx

CHANGELOG.md

@@ -5,6 +5,7 @@
 * [#2629](https://github.com/ruby-grape/grape/pull/2629): Refactor Router Architecture - [@ericproulx](https://github.com/ericproulx).
 * [#2633](https://github.com/ruby-grape/grape/pull/2633): Refactor API::Instance and reorganize DSL modules - [@ericproulx](https://github.com/ericproulx).
 * [#2636](https://github.com/ruby-grape/grape/pull/2636): Refactor router to simplify method signatures and reduce duplication - [@ericproulx](https://github.com/ericproulx).
+* [#2639](https://github.com/ruby-grape/grape/pull/2639): Refactor mime_types_for - [@ericproulx](https://github.com/ericproulx).
 * [#2638](https://github.com/ruby-grape/grape/pull/2638): Remove unnecessary path string duplication - [@ericproulx](https://github.com/ericproulx).
 * Your contribution here.
 

lib/grape/content_types.rb

@@ -22,10 +22,7 @@ def content_types_for(from_settings)
     def mime_types_for(from_settings)
       return MIME_TYPES if from_settings == Grape::ContentTypes::DEFAULTS
 
-      from_settings.each_with_object({}) do |(k, v), types_without_params|
-        # remove optional parameter
-        types_without_params[v.split(';', 2).first] = k
-      end
+      from_settings.invert.transform_keys! { |k| k.include?(';') ? k.split(';', 2).first : k }
     end
   end
 end