Verify phone number input in contact form

[MizukiTemma]

Motivation

Users can register a phone number in each contact. This field is currently CharField and there is no guarantee/check that the input value is valid as phone number.

Proposed Solution

• Decide what kind of input we accept. A phone number can be written in many ways: 0123456789, +49123456789, 0123/45679, 0123-456789, etc. we should take into consideration how the phone numbers are currently automatically formatted in the description field of contents. Convert contact phone numbers to international format #3383
• Show an error message if anything not acceptable is given in the field before saving (for example, string).

Alternatives

Leave as it is.

User Story

Additional Context

Design Requirements

Related Issues

[MizukiTemma]

@JoeyStk
Do you think this is still needed after #3383 ?

[JoeyStk]

I don't know yet, because we get an AttributeError when inputting any kind of phone number (0123456789, +49123456789). It says:
'Settings' object has no attribute 'DEFAULT_PHONE_NUMBER_COUNTRY_CODE'. I must have missed this during my review of the PR