Add an api to upload an image

[Vichy97]

Right now I need to do a lot of steps to upload from mobile. I need to:

• generate a uuid
• request a url from google url service with that uuid in the url
• upload the blob to that url
• make a mutation to include the tag for the area/climb i'm uploading to

This is a lot of steps and not very robust in the case of failure of any of the steps. It also will be very difficult to support uploading images while offline. We should have a single mutation that does all of this.