Allow configuring osiris data_dir in Cuttlefish config

This is the same as the `raft.data_dir` option but for Osiris' data
directory. Configuring this in Cuttlefish is nicer than the existing
`$RABBITMQ_STREAM_DIR` environment variable way of changing the dir.

Author: the-mikedavis

deps/rabbit/priv/schema/rabbit.schema

@@ -2776,6 +2776,19 @@ fun(Conf) ->
     end
 end}.
 
+{mapping, "stream.data_dir", "osiris.data_dir", [
+  {datatype, string}
+]}.
+
+{translation, "osiris.data_dir",
+    fun(Conf) ->
+        case cuttlefish:conf_get("stream.data_dir", Conf, undefined) of
+            undefined -> cuttlefish:unset();
+            Val       -> Val
+        end
+    end
+}.
+
 {mapping, "stream.read_ahead", "rabbit.stream_read_ahead",
     [{datatype, {enum, [true, false]}}]}.
 

deps/rabbit/test/config_schema_SUITE_data/rabbit.snippets

@@ -1253,6 +1253,16 @@ credential_validator.regexp = ^abc\\d+",
    [{rabbit, [
       {stream_read_ahead, false}
      ]}],
+   []},
+
+  %%
+  %% Stream data dir
+  %%
+  {stream_data_dir,
+   "stream.data_dir = /data/rabbitmq/stream",
+   [{osiris, [
+      {data_dir, "/data/rabbitmq/stream"}
+     ]}],
    []}
 
 ].