Generate a longer agentk token by default

See https://gitlab.com/gitlab-org/gitlab/-/issues/270218

app/models/clusters/agent_token.rb

@@ -3,7 +3,7 @@
 module Clusters
   class AgentToken < ApplicationRecord
     include TokenAuthenticatable
-    add_authentication_token_field :token, encrypted: :required
+    add_authentication_token_field :token, encrypted: :required, token_generator: -> { Devise.friendly_token(50) }
 
     self.table_name = 'cluster_agent_tokens'
 

changelogs/unreleased/use-longer-agentk-token.yml

+---
+title: Generate a longer Kuberntes Agent Token by default (was 20 characters, now 50)
+merge_request: 45620
+author:
+type: changed

spec/models/clusters/agent_token_spec.rb

@@ -14,5 +14,10 @@ RSpec.describe Clusters::AgentToken do
 
       expect(agent_token.token).to be_present
     end
+
+    it 'is at least 50 characters' do
+      agent_token = create(:cluster_agent_token)
+      expect(agent_token.token.length).to be >= 50
+    end
   end
 end