Draft: Instance Integrations test of shared module code

What does this MR do and why?

Mentions #499482 (closed)

[1] pry(main)> Integrations::Instance::Jenkins.create!

=> #<Integrations::Instance::Jenkins:0x00000001561f2f28


[4] pry(main)> Integrations::Jenkins.create!(group: Group.last)

=> #<Integrations::Jenkins:0x0000000137b121e0

[1] pry(main)> Integrations::Jira.create!(group: Group.last)

=> #<Integrations::Jira:0x00000001636b5a08

[2] pry(main)> Integrations::Instance::Jira.create!

=> #<Integrations::Instance::Jira:0x0000000162812a00

[4] pry(main)> Integrations::Instance::Jira.last.jira_tracker_data

=> #<Integrations::JiraTrackerData:0x000000015ac31cd8
 id: 12,

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app/models/concerns/integrations/has_web_hook.rb

@@ -7,6 +7,7 @@ module HasWebHook
     included do
       after_save :update_web_hook!, if: :activated?
       has_one :service_hook, inverse_of: :integration, foreign_key: :integration_id
+      has_one :service_hook, inverse_of: :instance_integration, foreign_key: :instance_integration_id, class_name: 'Integrations::Instance::Integration'
     end
 
     # Return the URL to be used for the webhook.