Merge branch '18755-fix-destroy-project-causes-post_decline_request-to-be-executed' into 'master'

Resolve "Destroying a project causes post_decline_request to be executed"

## What does this MR do?

Ensure we don't send "access request declined" to access requesters when a project is deleted.

## Are there points in the code the reviewer needs to double check?

I've created a service to decouple the notification sending from the AR model.

## Why was this MR needed?

Because there was an issue.

## What are the relevant issue numbers?

Fixes #18755, #18750.

## Does this MR meet the acceptance criteria?

- [x] No CHANGELOG needed.
- [x] Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4744

2 files changed, 28 insertions, 14 deletions

diff --git a/app/services/members/destroy_service.rb b/app/services/members/destroy_service.rb
new file mode 100644
index 00000000000..15358f80208
--- /dev/null
+++ b/app/services/members/destroy_service.rb
@@ -0,0 +1,21 @@
+module Members
+  class DestroyService < BaseService
+    attr_accessor :member, :current_user
+
+    def initialize(member, user)
+      @member, @current_user = member, user
+    end
+
+    def execute
+      unless member && can?(current_user, "destroy_#{member.type.underscore}".to_sym, member)
+        raise Gitlab::Access::AccessDeniedError
+      end
+
+      member.destroy
+
+      if member.request? && member.user != current_user
+        notification_service.decline_access_request(member)
+      end
+    end
+  end
+end
diff --git a/app/services/notification_service.rb b/app/services/notification_service.rb
index 19832a19b2b..590350a11e5 100644
--- a/app/services/notification_service.rb
+++ b/app/services/notification_service.rb
@@ -181,15 +181,16 @@ class NotificationService
     end
   end
 
-  # Project access request
-  def new_project_access_request(project_member)
-    mailer.member_access_requested_email(project_member.real_source_type, project_member.id).deliver_later
+  # Members
+  def new_access_request(member)
+    mailer.member_access_requested_email(member.real_source_type, member.id).deliver_later
   end
 
-  def decline_project_access_request(project_member)
-    mailer.member_access_denied_email(project_member.real_source_type, project_member.project.id, project_member.user.id).deliver_later
+  def decline_access_request(member)
+    mailer.member_access_denied_email(member.real_source_type, member.source_id, member.user_id).deliver_later
   end
 
+  # Project invite
   def invite_project_member(project_member, token)
     mailer.member_invited_email(project_member.real_source_type, project_member.id, token).deliver_later
   end
@@ -216,15 +217,7 @@ class NotificationService
     mailer.member_access_granted_email(project_member.real_source_type, project_member.id).deliver_later
   end
 
-  # Group access request
-  def new_group_access_request(group_member)
-    mailer.member_access_requested_email(group_member.real_source_type, group_member.id).deliver_later
-  end
-
-  def decline_group_access_request(group_member)
-    mailer.member_access_denied_email(group_member.real_source_type, group_member.group.id, group_member.user.id).deliver_later
-  end
-
+  # Group invite
   def invite_group_member(group_member, token)
     mailer.member_invited_email(group_member.real_source_type, group_member.id, token).deliver_later
   end