The following rules apply to secret names:

* Secret names can only contain alphanumeric characters (`[a-z]`, `[A-Z]`, `[0-9]`) or underscores (`_`). Spaces are not allowed.
* Secret names must not start with the `GITHUB_` prefix.
* Secret names must not start with a number.
* Secret names are not case-sensitive.
* Secret names must be unique at the level they are created at.