Allow users to change their phone number

[jasonaowen]

Currently, only Keycloak administrators can change a user's phone number. Instead, this should be self-serve via the account page.

[reefdog]

I was surprised not to find this option within Keycloak account self-management!

[bickelj]

With PhilanthropyDataCommons/service#959 the situation is slightly better: pdc-admin members in the PDC realm can change a phone number and those members do not have to be Keycloak administrators.