Canvassing: No indicator of user location on map

[richardolsson]

Description

The new canvassing feature contains a map for canvassers. For users to understand what place they're close to, there is a geolocation button that will pan to the location of the user as reported by the browser. But the feature only pans the map, it doesn't indicate the position on the map. This means that as soon as the user pans or zooms, all indication of where they are (physically) on the map is lost.

Steps to reproduce

1. Go to https://app.dev.zetkin.org/my/canvassassignments
2. Log in as testadmin@example.com (this assumes that this user has canvass assignments, which it does at the time of writing)
3. Go into any assignment
4. On the map, click the GPS button (bottom-most of the four map control buttons)
5. Approve the geolocation access request in your browser
6. Wait for the geolocation to work
7. After the map has been panned, pan around manually

Expected Behaviour

The map should pan automatically (step 6-7) to your location and your physical location should be indicated on the map, even as you pan around.

Actual Behaviour

The map is panned automatically to your location, but the location is not indicated on the map. So when you pan around, you lose track of where you are, physically.

Screenshots (if you have any)

Proposed solution

This will require some thinking about for how long to display the location, and whether to update it automatically if you walk around. We also need to come up with a design for the marker, so whoever takes this on will either need to come up with a suggestion, or wait for designers to define it.