Don't use the format detail if it maps directly

bookwyrm/connectors/abstract_connector.py

@@ -326,3 +326,11 @@ def infer_physical_format(format_text):
         if not matches:
             return None
         return matches[0]
+
+def unique_physical_format(format_text):
+    """ only store the format if it isn't diretly in the format mappings"""
+    format_text = format_text.lower()
+    if format_text in format_mappings:
+        # try a direct match, so saving this would be redundant
+        return None
+    return format_text