users can choose to receive password reset via SMS

[Zrrrpy]

Part of epic #1017, dependent on #1785, #1790, #1791, #1780, and #1782

AS a volunteer/supervisor/admin,
I WANT the option to receive a password reset link via SMS,
SO THAT I am not restricted by receiving it only via email.

How it works now

Right now, all users only have the option to receive a password reset link by email.

How it should work instead

All users should have the option to receive a password reset link via SMS.

Acceptance criteria

• on the "forgot password" page, there should be a field for mobile number
• the field should only accept numbers
• field should only accept mobile numbers that are the appropriate length of a US mobile number (ten digits without +1 in the front, 11 digits if 1 is included as the first digit)
• the text "or" should separate the email and mobile number fields so it is obvious the user only needs to enter one
• the phone number entered must already be associated with an existing user account
• clicking "send me reset password instructions" after entering an existing mobile number triggers an SMS notification containing a reset password link
• that SMS should read something like:
  Click here to reset your password on casavolunteetracking.org [link]
• clicking "send me password instructions" after entering a mobile number overrides previous opt-out preferences (so that the user can receive the one-time notification they are requesting)

[github-actions]

This issue has been open without changes for a long time! What's up?

[xihai01]

will work on this