Replace "/" in param-name with "_" during sanitizing

While sanitizing the params for filenames, this avoids creating
unwanted sub-dirs, when fields contain "/".

Fixes #17

funkwhale_cli/utils.py

@@ -83,6 +83,8 @@ def sanitize_recursive(value):
     else:
         if value and str(value).startswith("/"):
             value = str(value)[1:]
+        if isinstance(value, str):
+            value = value.replace("/", "_")
         return pathvalidate.sanitize_filepath(str(value))