Change MR approval rule api

Now endpoints are under approval_settings scope.

ee/app/models/approval_state.rb

@@ -51,7 +51,7 @@ class ApprovalState
   end
 
   def overall_approvals_required
-    @overall_approvals_required ||= [project.approvals_before_merge, merge_request.approvals_before_merge].max
+    @overall_approvals_required ||= [project.approvals_before_merge, merge_request.approvals_before_merge || 0].max
   end
 
   def approved?

ee/lib/api/merge_request_approvals.rb

@@ -53,7 +53,7 @@ module API
           success: ::EE::API::Entities::MergeRequestApprovalRules,
           hidden: true
         }
-        get 'approval_rules' do
+        get 'approval_settings' do
           merge_request = find_merge_request_with_access(params[:merge_request_iid])
 
           present merge_request.approval_state, with: ::EE::API::Entities::MergeRequestApprovalRules, current_user: current_user

ee/lib/ee/api/entities.rb

@@ -264,6 +264,7 @@ module EE
       # Decorates ApprovalState
       class MergeRequestApprovalRules < Grape::Entity
         expose :wrapped_approval_rules, as: :rules, using: MergeRequestApprovalRule
+        expose :overall_approvals_required, as: :fallback_approvals_required
       end
 
       # Decorates Project

ee/spec/requests/api/merge_request_approvals_spec.rb

@@ -484,7 +484,7 @@ describe "API::MergeRequestApprovals with approval_rule enabled" do
     end
   end
 
-  describe 'GET :id/merge_requests/:merge_request_iid/approval_rules' do
+  describe 'GET :id/merge_requests/:merge_request_iid/approval_settings' do
     let!(:rule) { create(:approval_merge_request_rule, merge_request: merge_request, approvals_required: 2, name: 'foo') }
 
     it 'retrieves the approval rules details' do
@@ -492,7 +492,7 @@ describe "API::MergeRequestApprovals with approval_rule enabled" do
       merge_request.approvals.create(user: approver)
       rule.users << approver
 
-      get api("/projects/#{project.id}/merge_requests/#{merge_request.iid}/approval_rules", user)
+      get api("/projects/#{project.id}/merge_requests/#{merge_request.iid}/approval_settings", user)
 
       expect(response).to have_gitlab_http_status(200)
       expect(json_response['rules'].size).to eq(1)
@@ -509,7 +509,7 @@ describe "API::MergeRequestApprovals with approval_rule enabled" do
       private_group = create :group, :private
       rule.groups << private_group
 
-      get api("/projects/#{project.id}/merge_requests/#{merge_request.iid}/approval_rules", user)
+      get api("/projects/#{project.id}/merge_requests/#{merge_request.iid}/approval_settings", user)
 
       expect(response).to have_gitlab_http_status(200)
       expect(json_response['rules'].size).to eq(1)