Shared content across namespaces

Update content ingests to use content from another namespace.
Ingests must be committed to make content available and the
client will see the sharing as an ingest which has already
been fully written to, but not completed.

Updated the database version to change the ingest record in
the database from a link key to an object with a link and
expected value. This expected value is used to indicate that
the content already exists and an underlying writer may
not yet exist.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

services/content/service.go

@@ -356,7 +356,7 @@ func (s *service) Write(session api.Content_WriteServer) (err error) {
 		// users use the same writer style for each with a minimum of overhead.
 		if req.Expected != "" {
 			if expected != "" && expected != req.Expected {
-				return status.Errorf(codes.InvalidArgument, "inconsistent digest provided: %v != %v", req.Expected, expected)
+				log.G(ctx).Debugf("commit digest differs from writer digest: %v != %v", req.Expected, expected)
 			}
 			expected = req.Expected
 
@@ -373,7 +373,7 @@ func (s *service) Write(session api.Content_WriteServer) (err error) {
 			// Update the expected total. Typically, this could be seen at
 			// negotiation time or on a commit message.
 			if total > 0 && req.Total != total {
-				return status.Errorf(codes.InvalidArgument, "inconsistent total provided: %v != %v", req.Total, total)
+				log.G(ctx).Debugf("commit size differs from writer size: %v != %v", req.Total, total)
 			}
 			total = req.Total
 		}