Expose suggestion commit message via project API

lib/api/entities.rb

@@ -335,6 +335,7 @@ class Project < BasicProjectDetails
       expose :remove_source_branch_after_merge
       expose :printing_merge_request_link_enabled
       expose :merge_method
+      expose :suggestion_commit_message
       expose :statistics, using: 'API::Entities::ProjectStatistics', if: -> (project, options) {
         options[:statistics] && Ability.allowed?(options[:current_user], :read_statistics, project)
       }

lib/api/helpers/projects_helpers.rb

@@ -46,6 +46,7 @@ module ProjectsHelpers
         optional :avatar, type: File, desc: 'Avatar image for project' # rubocop:disable Scalability/FileUploads
         optional :printing_merge_request_link_enabled, type: Boolean, desc: 'Show link to create/view merge request when pushing from the command line'
         optional :merge_method, type: String, values: %w(ff rebase_merge merge), desc: 'The merge method used when merging merge requests'
+        optional :suggestion_commit_message, type: String, desc: 'The commit message used to apply merge request suggestions'
         optional :initialize_with_readme, type: Boolean, desc: "Initialize a project with a README.md"
         optional :ci_default_git_depth, type: Integer, desc: 'Default number of revisions for shallow cloning'
         optional :auto_devops_enabled, type: Boolean, desc: 'Flag indication if Auto DevOps is enabled'
@@ -119,6 +120,7 @@ def self.update_params_at_least_one_of
           :visibility,
           :wiki_access_level,
           :avatar,
+          :suggestion_commit_message,
 
           # TODO: remove in API v5, replaced by *_access_level
           :issues_enabled,