Prevent creating guest if email is in LDAP search terms

[PVince81]

To be discussed @dercorn @butonic @tomneedham @pmaier1

This is the next step after #168

[PVince81]

@davitol can you check if this already works with guests master and stable10 ?

It is likely that the frontend is already removing the "Add guest" entry when exact-matching a secondary email address. I don't have the LDAP env to test this. Depending on the result we can adjust priority.

[tomneedham]

search terms should not affect user creation?? Yes - it could result in duplicate results in a search dialog but terms should not be distinct.

[PVince81]

@tomneedham if one of the search terms contains a secondary email address, we likely don't want to create a guest user with said secondary email address.

[PVince81]

@davitol has confirmed that the JS properly removes "Add guest" when inputting a oc_account_terms entry which is an email address.

This is already enough for proper functioning.

For the sake of completion, we also need to fix the backend to prevent creation of guests in case someone would call the API directly.