added phone number regex validator.

[AlecsGherghel]

What does it fix?

Closes #218

Added a new validator for phone field from NGO model.

[AlecsGherghel]

@catileptic Do we want to use the same validation logic for all phone fields?

I see that we also have:

• PaymentOrder.phone
• NGOHelper.phone
• PersonalRequest.phone
• RegisterNGORequest.phone

[catileptic]

Let's not merge this yet. The regexp doesn't support numbers that start with anything other than +4 (or doesn't have the country code).

[aramboi]

Rather than adding our custom regex in the models, maybe it would be better to use a Django app like https://github.com/stefanfoulis/django-phonenumber-field that lets you choose from one of the standardized formats. Underneath it relies on a python port of the Google phone number library used in Android and it has support for national and international number formatting. Example from the readme:

>>> phonenumbers.format_number(x, phonenumbers.PhoneNumberFormat.NATIONAL)
'020 8366 1177'
>>> phonenumbers.format_number(x, phonenumbers.PhoneNumberFormat.INTERNATIONAL)
'+44 20 8366 1177'
>>> phonenumbers.format_number(x, phonenumbers.PhoneNumberFormat.E164)
'+442083661177'

[AlecsGherghel]

@aramboi That looks good! At the time of creating this PR I was looking for a quick turnaround without adding a new project dependency.

But now that the project is doing well live, I think that relying on existing libraries sounds like a great idea :)

I'll be closing this in the meantime and when there's a decision around the path going forward I'll either re-open a different one or maybe someone else will do it.