Don't show primary keys as integers

[dternyak]

Wherever we expose primary keys, we should instead use a hash/uuid-esque identifier/non incrementing integer.

This includes:

• API Responses
• URL parameters

[wbobeirne]

Just a heads up that proposal contributions currently use ID as the index for address derivation. We'll either need to make a new column for that, or keep them numeric and less than 2^31.

[AMStrix]

I think I prefer the simplicity of using straight up UUIDs as IDs everywhere.

But, I'd like to just drop a note on another possible approach. We could use a marshmallow custom field to deserialize/serialize IDs using simple encryption. Something like hashids lib might work well.

[wbobeirne]

Ah, there's one thing I didn't think to test here, which is how discovery of funds works with bip 32. If it's sequential, we'll want to revert this change on contributions alone, or switch them to have their own address_index column that's auto incrementing separate of the id.

[wbobeirne]

Opened #301 for the above comment