Always persist processed of CommitStatus

Since the same instance can go through multiple
status transitions the subsequent changes to `processed`
can be lost since the object is not refresh to exact
DB state.

Always consider processed as a changed value
and persist its current value.

app/models/commit_status.rb

@@ -94,6 +94,11 @@ class CommitStatus < ApplicationRecord
   end
 
   before_save if: :status_changed?, unless: :importing? do
+    # we mark `processed` as always changed:
+    # another process might change its value and our object
+    # will not be refreshed to pick the change
+    self.processed_will_change!
+
     if Feature.disabled?(:ci_atomic_processing, project)
       self.processed = nil
     elsif latest?

spec/models/commit_status_spec.rb

@@ -96,6 +96,21 @@ describe CommitStatus do
 
         it { is_expected.to be_truthy }
       end
+
+      it "processed state is always persisted" do
+        commit_status.update!(retried: false, status: :pending)
+
+        # another process does mark object as processed
+        CommitStatus.find(commit_status.id).update_column(:processed, true)
+
+        # subsequent status transitions on the same instance
+        # always saves processed=false to DB even though
+        # the current value did not change
+        commit_status.update!(retried: false, status: :running)
+
+        # we look at a persisted state in DB
+        expect(CommitStatus.find(commit_status.id).processed).to eq(false)
+      end
     end
   end