git-lfs: report returned data as 'application/vnd.git-lfs+json' instead of plain json

git-lfs: always validate uploaded files size. In case of bad uploads we want the client to re-try the LFS object upload. Else we can end up with wrong sized OIDs uploaded and reported as OK.

release: merge back stable branch into default

Added tag v4.7.1 for changeset 57f527e0646d

release: Finish preparation for 4.7.1

release: updated pip2nix output for 4.7.1

release: Start preparation for 4.7.1

dependencies: bumped internal libs to latest versions. - traitlets - ipython-genutils - prompt-toolkit

nix: bumped internal version inside default.nix

release: Bump version 4.7.0 to 4.8.0