Add kekRenameFormat to exporter configs (#57)

Add property kekRenameFormat to exporter configs.  This
allows for renaming keks during schema linking, and can take
the form of `${kek}-suffix` for example, similar to how
subjectRenameFormat uses the template `${subject}`

api/openapi.yaml

@@ -4371,6 +4371,8 @@ components:
           type: string
         context:
           type: string
+        kekRenameFormat:
+          type: string
         subjectRenameFormat:
           type: string
         config:
@@ -4411,6 +4413,8 @@ components:
           type: string
         context:
           type: string
+        kekRenameFormat:
+          type: string
         subjectRenameFormat:
           type: string
         config:
@@ -4469,6 +4473,8 @@ components:
           type: string
         context:
           type: string
+        kekRenameFormat:
+          type: string
         subjectRenameFormat:
           type: string
         config: