Add GKeyFile credentials storage using headless mode
This commit is based on !107 (merged).
According to #92 (comment 1487536), we need other ways to store credentials instead of keyring for headless mode, and in !108 (merged) we have a TPM backend, and a plain text fallback is mentioned in that MR. This MR adds an implementation via GKeyFile.
This is just a draft and any suggestions are welcome.
Edited by Alynx Zhou