Add necessary translators to peer handler context

BasePeer handler currently changes any '-' characters
in app databag keys to '_'. Handle '/' and '.' as well.
Charm microceph uses app databag keys like
'microceph/0,join_token'

Change-Id: I6091ba503e8711fcc6a43f672cfecc01eff44561

ops-sunbeam/ops_sunbeam/relation_handlers.py

@@ -584,8 +584,9 @@ class BasePeerHandler(RelationHandler):
     def context(self) -> dict:
         """Return all app data set on the peer relation."""
         try:
+            translators = str.maketrans({"/": "_", ".": "_", "-": "_"})
             _db = {
-                k.replace("-", "_"): v
+                k.translate(translators): v
                 for k, v in self.interface.get_all_app_data().items()
             }
             return _db