Empty NameID values were stored as '' and occupied the
unique saml_subject index, causing duplicate-key failures
on later logins. Reject blank NameIDs during assertion
validation, return a clear error when a NameID is already
linked to another account, and stop returning internal
errors from the SAML consume endpoint.
Signed-off-by: Sacha Al Himdani <sacha@probo.com>
bcd05a2e55