Add ability to set approvals_before_merge for project through the API

changelogs/unreleased-ee/approvals_required_api.yml

+---
+title: Add ability to set approvals_before_merge for project through the API
+merge_request: 
+author: 

lib/api/entities.rb

@@ -106,6 +106,7 @@ module API
       expose :repository_storage, if: lambda { |_project, options| options[:user].try(:admin?) }
       expose :only_allow_merge_if_build_succeeds
       expose :request_access_enabled
+      expose :approvals_before_merge
     end
 
     class Member < UserBasic
@@ -262,9 +263,11 @@ module API
       expose :merge_status
       expose :diff_head_sha, as: :sha
       expose :merge_commit_sha
+
       expose :subscribed do |merge_request, options|
         merge_request.subscribed?(options[:current_user])
       end
+
       expose :user_notes_count
       expose :approvals_before_merge
       expose :should_remove_source_branch?, as: :should_remove_source_branch

lib/api/projects.rb

@@ -261,6 +261,7 @@ module API
       #   public_builds (optional)
       #   repository_storage (optional)
       #   lfs_enabled (optional)
+      #   approvals_before_merge (optional) - how many approvers should approve merge request by default
       # Example Request
       #   PUT /projects/:id
       put ':id' do
@@ -281,7 +282,8 @@ module API
                                      :shared_runners_enabled,
                                      :snippets_enabled,
                                      :visibility_level,
-                                     :wiki_enabled]
+                                     :wiki_enabled,
+                                     :approvals_before_merge]
         attrs = map_public_to_visibility_level(attrs)
         authorize_admin_project
         authorize! :rename_project, user_project if attrs[:name].present?

spec/requests/api/projects_spec.rb

@@ -947,6 +947,15 @@ describe API::API, api: true  do
         expect(json_response['request_access_enabled']).to eq(false)
       end
 
+      it 'updates approvals_before_merge' do
+        project_param = { approvals_before_merge: 3 }
+
+        put api("/projects/#{project.id}", user), project_param
+
+        expect(response).to have_http_status(200)
+        expect(json_response['approvals_before_merge']).to eq(3)
+      end
+
       it 'updates path & name to existing path & name in different namespace' do
         project_param = { path: project4.path, name: project4.name }
         put api("/projects/#{project3.id}", user), project_param