Replace enable_ssl_verification assignment

with stub method which also removes that unused key.

Add API param back

app/models/project_services/buildkite_service.rb

@@ -8,7 +8,6 @@ class BuildkiteService < CiService
   ENDPOINT = "https://buildkite.com"
 
   prop_accessor :project_url, :token
-  boolean_accessor :enable_ssl_verification
 
   validates :project_url, presence: true, public_url: true, if: :activated?
   validates :token, presence: true, if: :activated?
@@ -19,6 +18,15 @@ class BuildkiteService < CiService
     %w(push merge_request tag_push)
   end
 
+  # Since SSL verification will always be enabled for Buildkite,
+  # we no longer needs to store the boolean.
+  # This is a stub method to work with deprecated API param.
+  # TODO: remove enable_ssl_verification after 14.0
+  # https://gitlab.com/gitlab-org/gitlab/-/issues/222808
+  def enable_ssl_verification=(_value)
+    self.properties.delete('enable_ssl_verification') # Remove unused key
+  end
+
   def webhook_url
     "#{buildkite_endpoint('webhook')}/deliver/#{webhook_token}"
   end

lib/api/helpers/services_helpers.rb

@@ -248,8 +248,14 @@ module API
               name: :project_url,
               type: String,
               desc: 'The Buildkite pipeline URL'
+            },
+            {
+              required: false,
+              name: :enable_ssl_verification,
+              type: Boolean,
+              desc: 'DEPRECATED: This parameter has no effect since SSL verification will always be enabled'
             }
-          ],
+        ],
           'campfire' => [
             {
               required: true,

spec/models/project_services/buildkite_service_spec.rb

@@ -57,12 +57,13 @@ RSpec.describe BuildkiteService, :use_clean_rails_memory_store_caching do
     end
 
     it 'always activates SSL verification after saved' do
+      service.create_service_hook(enable_ssl_verification: false)
+
       service.enable_ssl_verification = false
       service.active = true
 
-      service.save!
-
-      expect(service.reload.enable_ssl_verification).to be true
+      expect { service.save! }
+        .to change { service.service_hook.enable_ssl_verification }.from(false).to(true)
     end
 
     describe '#webhook_url' do