The four boolean OIDC provider fields (emailfallback, usernamefallback,
forceuserinfo, requireavailability) were parsed with a strict .(bool)
type assertion. That works for YAML/JSON config where leaves are native
bools, but fails for every other input path: env vars always arrive as
strings, and GetConfigValueFromFile (used by the *.file Docker secret
convention) also always returns strings. The assertion would silently
zero the field for emailfallback and usernamefallback, and log an error
and zero the field for forceuserinfo and requireavailability, which is
what #2599 reports.
Extract a small parseBoolField helper that accepts both native bools and
strings (via strconv.ParseBool) and logs a parse error from each call
site. This also fixes the previously-silent drop of stringified
emailfallback / usernamefallback values — those now log an error if the
input is garbage, matching the behaviour of the other two fields.
Fixes#2599
ced7ebd97f