fix(schema-diff): Include foreign key constraints in diff

With the change to report changes to constraints instead of all of the
post-data section, foreign key constraints where no longer captured in
the diff. This now extracts the foreign key constraints and generates a
diff of them between versions.

Blame: b6d58d0c42

.github/workflows/schema-diff.yml

@@ -76,6 +76,9 @@ jobs:
 
           #### Constraints
           $(getdiff .schema-diff/constraints.diff)
+
+          #### Foreign Key Constraints
+          $(getdiff .schema-diff/fk_constraints.diff)
           EOF
 
           # Parse it through jq to build a valid json object.