maintainer search: lookup via package name by default and binary as fallback

This is faster in best case since the binary search does not need
to be executed on the server.

It also finds package names where no binary with that name exists.
(as for some multibuild cases)

osc/core.py

@@ -6809,12 +6809,21 @@ def search(apiurl, queries=None, **kwargs):
         res[urlpath] = ET.parse(f).getroot()
     return res
 
-def owner(apiurl, binary, mode="binary", attribute=None, project=None, usefilter=None, devel=None, limit=None):
+def owner(apiurl, search_term=None, mode="binary", attribute=None,
+          project=None, usefilter=None, devel=None, limit=None, binary=None):
     """
     Perform a binary package owner search. This is supported since OBS 2.4.
     """
+
+    # binary is just for API backward compatibility
+    if not ((search_term is None) ^ (binary is None)):
+        raise ValueError('Either specify search_term or binary')
+    elif binary is not None:
+        search_term = binary
+ 
     # find default project, if not specified
-    query = { mode: binary }
+    # mode can be "binary" or "package" atm
+    query = { mode: search_term }
     if attribute:
         query['attribute'] = attribute
     if project: