Create Address model & migrate HelpRequest and Volunteer to use it

[stavlocker]

Related component: HelpRequest, Volunteer

Description

Currently Volunteer has the following fields to represent the address:

• city - a City model (options prefilled by cities.json with obsolete corrdinates)
• address - a string representing the street, house number, apt. number but in arbitrary user-picked order (that we later use APIs with NLP to turn into coordinates)
• location_address_x, location_address_y - the lat/long retrieved from the API from the city + address

These also exist in HelpRequest (and if they don't they should to work in the current format).

Instead this should be one model called Address that contains:

• city
• street (optional)
• house no. (optional)
• apt. no. (optional)
• longtitude
• latitude

And HelpRequest & Volunteer should contain one address field with a foreignkey to the Address model.

The current data in the production DB should be migrated to use this new API

---

Prerequisites

[Make sure you've done the following before posting your issue:]

• [ ] I have filled in the correct labels (fill at least one of bug/enhancement)
• [ ] I have searched for duplicate issues and found none
• [ ] My issue is phrased as a task - it's clear what needs to be done here.

[stavlocker]

Put on hold until new system is stabilized