Update project's fallback_approvals_required

Use existing project PUT to update

ee/app/models/ee/project.rb

@@ -120,6 +120,8 @@ module EE
 
       accepts_nested_attributes_for :tracing_setting, update_only: true, allow_destroy: true
       accepts_nested_attributes_for :alerting_setting, update_only: true
+
+      alias_attribute :fallback_approvals_required, :approvals_before_merge
     end
 
     class_methods do

ee/lib/api/project_approval_rules.rb

@@ -22,29 +22,6 @@ module API
           present user_project, with: EE::API::Entities::ProjectApprovalRules, current_user: current_user
         end
 
-        desc 'Update fallback approvals required' do
-          detail 'Private API subject to change'
-          success ::API::Entities::Project
-        end
-        params do
-          requires :fallback_approvals_required, as: :approvals_before_merge, type: Integer, desc: 'The total number of required approvals in case of fallback'
-        end
-        put do
-          authorize! :admin_project, user_project
-
-          result = ::Projects::UpdateService.new(user_project, current_user, declared_params).execute
-
-          if result[:status] == :success
-            present(
-              user_project,
-              with: ::API::Entities::Project,
-              user_can_admin_project: can?(current_user, :admin_project, user_project)
-            )
-          else
-            render_validation_error!(user_project)
-          end
-        end
-
         segment 'rules' do
           desc 'Create new approval rule' do
             detail 'Private API subject to change'

ee/lib/ee/api/projects.rb

@@ -20,6 +20,7 @@ module EE
             optional :mirror_overwrites_diverged_branches, type: Grape::API::Boolean, desc: 'Pull mirror overwrites diverged branches'
             optional :import_url, type: String, desc: 'URL from which the project is imported'
             optional :packages_enabled, type: Grape::API::Boolean, desc: 'Enable project packages feature'
+            optional :fallback_approvals_required, type: Integer, desc: 'Overall approvals required when no rule is present'
           end
 
           def apply_filters(projects)

ee/spec/requests/api/project_approval_rules_spec.rb

@@ -74,42 +74,6 @@ describe API::ProjectApprovalRules do
     end
   end
 
-  describe 'PUT /projects/:id/approval_settings' do
-    let(:url) { "/projects/#{project.id}/approval_settings" }
-
-    shared_examples_for 'a user with access' do
-      context 'when sending json data' do
-        it 'updates approvals_before_merge' do
-          expect do
-            put api(url, current_user), params: { fallback_approvals_required: 1 }.to_json, headers: { CONTENT_TYPE: 'application/json' }
-          end.to change { project.reload.approvals_before_merge }.from(0).to(1)
-
-          expect(response).to have_gitlab_http_status(200)
-        end
-      end
-    end
-
-    context 'as a project admin' do
-      it_behaves_like 'a user with access' do
-        let(:current_user) { user }
-      end
-    end
-
-    context 'as a global admin' do
-      it_behaves_like 'a user with access' do
-        let(:current_user) { admin }
-      end
-    end
-
-    context 'as a random user' do
-      it 'returns 403' do
-        put api(url, user2), { fallback_approvals_required: 1 }.to_json, { CONTENT_TYPE: 'application/json' }
-
-        expect(response).to have_gitlab_http_status(403)
-      end
-    end
-  end
-
   describe 'POST /projects/:id/approval_settings/rules' do
     let(:current_user) { user }
     let(:params) do