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What does this MR do and why?

Related issue: Automated/web commits (merge or web IDE commits... (#19185 - closed)

It is now possible to configure Gitaly to use signing_key to sign commits created by Gitaly:

GPG

• Add support for Gitaly GPG signing (omnibus-gitlab!6294 - merged)
• feat(gitaly-git2go): sign commits with OpenPGP key (gitaly!4802 - merged)

SSH

• Add support for commit signing using SSH (gitaly!5408 - merged). It has been implemented in order to provide a FIPS-compliant configuration: gitaly!5408 (comment 1288435487). The package that is used for GPG is not FIPS-compliant: Remove go-crypto dependency for FIPS compliance (gitaly#4594).

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Steps to verify

1. Modify Gitaly config (gitaly.config.toml or gitaly-0.praefect.toml file) and specify git.signing_key option:

# # Git settings
[git]
use_bundled_binaries = true
catfile_cache_size = 10
ignore_gitconfig = true
signing_key = "<path-to-gdk>/gitaly/internal/git2go/testdata/signing_ssh_key_ed25519"

signing_ssh_key_ecdsa, signing_ssh_key_ed25519, signing_ssh_key_rsa, signing_gpg_key_rsa from internal/git2go/testdata are used in tests and good enough to be used for testing, but also new keys can be generated.

2. Open a project and edit a file via Web UI

3. The created commit should be Verified