Make email comparison for SAML case insensitive

[fastlorenzo]

Email comparison when doing SSO with SAML is currently case sensitive.
However, email addresses should be treated as case insensitive.

This PR makes sure that:

1. Email address of each user is saved as lowercase in the database
2. Email address received from IDP when doing SSO is converted to lowercase prior to comparison

[eric-intuitem]

LGTM, but we need to adapt functional tests. @nas-tabchiche ?

[ab-smith]

we will merge it after the Ebios RM sprint and fix the test on our side before releasing

[fastlorenzo]

we will merge it after the Ebios RM sprint and fix the test on our side before releasing

Thanks, no worries, now that we know the current behavior we've fixed it in the IDP by forcing lowercase email conversion