Receptive cluster agents

What does this MR do and why?

Draft: Receptive cluster agents

Changelog: added

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Related to #463427 (closed) #463426 (closed)

app/models/clusters/agents/url_configuration.rb

@@ -43,6 +43,9 @@ class UrlConfiguration < ApplicationRecord
         revoked: 1
       }
 
+      after_create :set_agent_receptive!
+      after_destroy :unset_agent_receptive!
+
       private
 
       def public_key_auth?
@@ -52,6 +55,14 @@ def public_key_auth?
       def certificate_auth?
         !public_key_auth?
       end
+
+      def set_agent_receptive!
+        agent.update!(is_receptive: true)
+      end
+
+      def unset_agent_receptive!
+        agent.update!(is_receptive: false)
+      end
     end
   end
 end