Allow atoms-as-keys (input) while respecting the remote system

It's probably better to spec with atoms, since the
keys will be known, but the system appears to not
work if we send in atoms, so we convert these to
binaries before going to Hex.pm

src/hex_api_release.erl

@@ -143,10 +143,18 @@ delete(Config, Name, Version) when is_map(Config) and is_binary(Name) and is_bin
 %% '''
 %% @end
 -spec retire(hex_core:config(), binary(), binary(), retirement_params()) -> hex_api:response().
-retire(Config, Name, Version, Params) when
+retire(Config, Name, Version, Params0) when
     is_map(Config) and is_binary(Name) and is_binary(Version)
 ->
     Path = hex_api:build_repository_path(Config, ["packages", Name, "releases", Version, "retire"]),
+    Params = maps:fold(
+        fun (K, V, AccIn) ->
+            AccIn#{
+                atom_to_binary(K) => V
+            }
+        end,
+        #{},
+        Params0),
     hex_api:post(Config, Path, Params).
 
 %% @doc