feat: topo data API

[btmccord]

We need the ability to to assign and retrieve a JSON object to photos/photo tags for the topo feature

[vnugent]

Do you have some sample data so that we can figure out how to store/retrieve it in the backend?

[btmccord]

Yep. Here you go

testdata.json

[btmccord]

I would think we can just store it as a string. The paper import function works with a string and the export function returns a JSON object or string. See http://paperjs.org/reference/path/#exportjson

[vnugent]

do you expect the internal structure to change? Another word should we store a version number along with the data?

[btmccord]

I think its likely to change structure, especially as we implement new features. A version number seems like a good idea. Although the version could also be put into the topo data itself, which might be better?

[vnugent]

Sure. We can make it an internal field for now. The version can help the frontend rendering code differentiate changes.