Error reference
Apple signing errors, and how to actually fix them
One page per error message, written for the moment you have pasted the string into a search box and your build is broken. Each page opens with the verbatim message and the short answer, then explains the cause and the fix for both local machines and CI runners.
codesign wants to access key in your keychain
macOS is asking for permission before letting codesign use the private key. Harmless locally, fatal on CI, where nobody is there to click the button.
keychainSee the fix
Xcode couldn't find any provisioning profiles matching
Xcode looked for a development provisioning profile covering your bundle ID and found nothing usable, so it stopped before building.
XcodeSee the fix
Failed to register bundle identifier
Apple refused to register the App ID because that bundle identifier is already claimed, either by another team or by an account you have forgotten about.
XcodeSee the fix