Function authenticate

authenticate(opts: AuthenticateOptions): Promise<LdapEntry | null>
Authenticates a user by the bind-search-bind pattern.

Connects and binds as the service account (LdapConnectOptions.bindDN / AuthenticateOptions.bindPassword), or anonymously when no bindDN is given; searches under base for the entry matching userFilter (capped at one result); then re-binds as that entry's DN with the user's AuthenticateOptions.password. The session is always closed before returning.
Parameters
- opts: AuthenticateOptions
  Connection settings, the user lookup, and the candidate password.
Returns Promise<LdapEntry | null>
The matched entry on a successful password bind, or null when no entry matches or the password is wrong.
Throws
If the connection or TLS upgrade fails.

Throws
If the service-account bind is rejected (a wrong user password returns null instead).

Throws
If the server misbehaves during search or bind.

Since
1.0.2
Example
```
const entry = await authenticate({
  hostname: 'ldap.example.org',
  bindDN: 'cn=admin,dc=example,dc=org',
  bindPassword: 'service-secret',
  base: 'ou=people,dc=example,dc=org',
  userFilter: eq('uid', 'jdoe'),
  password: 'the-user-password'
});
if (entry) {
  // authenticated; entry.dn is the bound user
}
```
- Defined in src/ldap/index.ts:304