Add note that management command changes may affect other repos.

DEVELOPERS.md

@@ -536,6 +536,10 @@ interfaces can be changed, through coordination with the relevant teams.
 Except where mentioned otherwise, URLs are relative to the root of the
 Job Server API endpoint (https://jobs.opensafely.org/api/v2 in production).
 
+Management commands may also be used in other repos' tooling and CI. If you
+change their API, check if they're used elsewhere and whether the change might
+be breaking for the other repo.
+
 ### Job Runner interface
 
 [Job Runner] is a container that runs in a secure backend. It executes