Certain issues are too big to be handled in a single PR. These issues are tagged with label "epic" either by the developer or the tech lead.
Divide the original problem into multiple issues.
Each sub-issue should mention
Ref issue ####.
In this way, Github will automatically link a child issue
with its epic issue.
Now, work on these child issues and send PR to close these child issues.
Once all the sub-issues are closed, then assign the epic issue to a QA person. An issue tagged with "epic" should never be closed by a PR. It should be closed manually by a QA.