FEATURE: Prevents assign notification & change status on solved

Relates to this [topic](https://meta.discourse.org/t/assign-plugin-for-informatica/256974/94)

Add an event listener to `accepted_solution` event

Add `assigns_reminder_assigned_topics_query` modifier to not notify if
`prevent_assign_notification` setting is on.

Add settings to prevent assign notification and change status on solved

app/lib/plugin_initializer.rb

@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+module DiscourseSolved
+  class PluginInitializer
+    attr_reader :plugin
+
+    def initialize(plugin)
+      @plugin = plugin
+    end
+
+    def apply_plugin_api
+      # this method should be overridden by subclasses
+      raise NotImplementedError
+    end
+  end
+
+  class AssignsRemainderForTopicsQuery < PluginInitializer
+    def apply_plugin_api
+      plugin.register_modifier(:assigns_reminder_assigned_topics_query) do |query|
+        next query if !SiteSetting.prevent_assign_notification
+        query.where(
+          "topics.id NOT IN (
+            SELECT topic_id
+            FROM topic_custom_fields
+            WHERE name = 'accepted_answer_post_id'
+          )",
+        )
+      end
+    end
+  end
+end

config/locales/server.en.yml

@@ -11,6 +11,9 @@ en:
     solved_topics_auto_close_hours: "Auto close topic (n) hours after the last reply once the topic has been marked as solved. Set to 0 to disable auto closing."
     show_filter_by_solved_status: "Show a dropdown to filter a topic list by solved status."
     notify_on_staff_accept_solved: "Send notification to the topic creator when a post is marked as solution by a staff."
+    prevent_assign_notification: "Prevent notification from discourse-assign for solved topics."
+    assign_to_status_on_solved: "Enable assigning a status when a topic is solved. Requires discourse-assign plugin."
+    status_to_assign_on_solved: "The status to assign when a topic is solved."
     disable_solved_education_message: "Disable education message for solved topics."
     accept_solutions_topic_author: "Allow the topic author to accept a solution."
     solved_add_schema_markup: "Add QAPage schema markup to HTML."

config/settings.yml

@@ -32,6 +32,13 @@ discourse_solved:
     client: true
   notify_on_staff_accept_solved:
     default: false
+  prevent_assign_notification:
+    default: false
+  assign_to_status_on_solved:
+    default: false
+  status_to_assign_on_solved:
+    type: string
+    default: "Done"
   disable_solved_education_message:
     default: false
   accept_solutions_topic_author:

plugin.rb

@@ -622,4 +622,13 @@ def self.skip_db?
       end
     end
   end
+
+  if defined?(DiscourseAssign) && SiteSetting.assign_to_status_on_solved
+    on(:accepted_solution) do |post|
+      Assigner.new(post.topic, post.acting_user).assign(
+        post.acting_user,
+        status: SiteSetting.status_to_assign_on_solved,
+      )
+    end
+  end
 end