Add support for sha256 repositories

[kimsondrup]

Right now there is no support for sha256 repositories so the following example fails

ssh soft repo create hello-sha256
echo "# hello-sha256" >> README.md
git init --object-format=sha256
git add README.md
git commit -m "first commit"
git branch -M main
git remote add origin ssh://soft/hello-sha256
git push -u origin main

fatal: the receiving end does not support this repository's hash algorithm
fatal: the remote end hung up unexpectedly
Error: something went wrong

Error from log

2023-11-07 10:34:58 ERRO ssh: failed to handle git service service=git-receive-pack err="exit status 128" repo=hello-sha256

I would like soft-serve to also support sha256 repositories 🙏

[kimsondrup]

Right now both Gitea and GitLab is working on sha256 support so to me it seems fitting for soft-serve to also have support for this in the future.