Move create/destroy actions for api/v1/statuses to namespace (#3678)

Each of mute, favourite, reblog has been updated to:

- Have a separate controller with just a create and destroy action
- Preserve historical route names to not break the API
- Mild refactoring to break up long methods

app/controllers/api/v1/statuses/mutes_controller.rb

@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+class Api::V1::Statuses::MutesController < Api::BaseController
+  include Authorization
+
+  before_action -> { doorkeeper_authorize! :write }
+  before_action :require_user!
+  before_action :set_status
+  before_action :set_conversation
+
+  respond_to :json
+
+  def create
+    current_account.mute_conversation!(@conversation)
+    @mutes_map = { @conversation.id => true }
+
+    render 'api/v1/statuses/show'
+  end
+
+  def destroy
+    current_account.unmute_conversation!(@conversation)
+    @mutes_map = { @conversation.id => false }
+
+    render 'api/v1/statuses/show'
+  end
+
+  private
+
+  def set_status
+    @status = Status.find(params[:status_id])
+    authorize @status, :show?
+  rescue Mastodon::NotPermittedError
+    # Reraise in order to get a 404 instead of a 403 error code
+    raise ActiveRecord::RecordNotFound
+  end
+
+  def set_conversation
+    @conversation = @status.conversation
+    raise Mastodon::ValidationError if @conversation.nil?
+  end
+end