lib/zodb/zurl_normalize_main += explicit filtering depending on scheme

In the old source code we already filtered NEO URI by dropping
credentials, but we applied this filter to any URI, not only the NEO
one. This patch adds a mechanism to apply various filter according to
the specific storage type. Starting with this new patch,
'zurl_normalize_main' also refuses to normalize an URI with an unknown
scheme.

lib/zodb.py

@@ -455,12 +455,34 @@ def _is_ipv6(host):
 #
 #   neos://ca=zzz@def:2,abc:1/cluster   ->  neos://abc:1,def:2/cluster
 def zurl_normalize_main(zurl):
+    scheme, netloc, path, query, frag = urlsplit(zurl)
+    try:
+        # Normalization depends on the storage backend (there is no standardized
+        # zodburi scheme among ZODB storages).
+        f = _zurl_normalize_registry[scheme.lower()]
+    except KeyError:
+        raise NotImplementedError("can't normalize zurl with scheme %s" % scheme)
+    return urlunsplit(f(scheme, netloc, path, query, frag))
+
+# _znormalizer registers func f for zurl_normalize to use as scheme handler.
+_zurl_normalize_registry = {}  # scheme -> normalization func
+def _znormalizer(scheme, f):
+    assert scheme not in _zurl_normalize_registry
+    _zurl_normalize_registry[scheme] = f
+
+# Supported storages, but no normalization applied yet (TODO).
+_znormalizer('file', lambda *args: args)
+_znormalizer('zeo',  lambda *args: args)
+_znormalizer('demo', lambda *args: args)
+
+
+def _znormalize_neo(scheme, netloc, path, query, frag):
     # remove credentials from zurl.
     # The same database can be accessed from different clients with different
     # credentials, but we want to map them all to the same single WCFS
     # instance.
-    scheme, netloc, path, query, frag = urlsplit(zurl)
-    if '@' in netloc:
-        netloc = netloc[netloc.index('@')+1:]
-    zurl = urlunsplit((scheme, netloc, path, query, frag))
-    return zurl
+    if "@" in netloc:
+        netloc = netloc[netloc.index("@") + 1 :]
+    return (scheme, netloc, path, query, frag)
+_znormalizer('neo',  _znormalize_neo)
+_znormalizer('neos', _znormalize_neo)