[FEATURE] Add support for docker secrets for ldap - TINYAUTH_LDAP_BINDPASSWORDFILE

[Rycochet]

Is your feature request related to a problem? Please describe.

Currently you have to pass a plain text password as an env variable - TINYAUTH_LDAP_BINDPASSWORD - this means the password is visible to anything with docker socket access.

LLDAP itself supports this already with LLDAP_LDAP_USER_PASS_FILE

Describe the solution you'd like.

Add support to pass a file as an alternative - TINYAUTH_LDAP_BINDPASSWORDFILE

• I confirm this request was written by me and not generated by an LLM or AI assistant.