Change authentication to use subject value

It is low priority, but considered better practice to use the token's subject value ("sub" attribute) for identifying users when authenticating rather than "bceif_user_guid" and "idir_user_guid".

**Purpose**
To improve security.

**Acceptance Criteria**
- [ ] Both portal and ALCS authentication uses "sub" value for authentication rather than "bceid_user_guid" and "idir_user_guid"

**Additional context**
- This issue was a result of #2330
- https://openid.net/specs/openid-connect-core-1_0.html#SubjectIDTypes

No files or tests are named; start by locating the portal and ALCS authentication entry points and review issue #2330 for context. Check the OpenID Connect SubjectIDTypes specification, then verify that both authentication paths use the token's "sub" value and no longer use the two GUID attributes.

Written by the indexing model from the issue text.