Figure out how to handle previews

Possibilities:

• Store in the database as base64-encoded binary blob. Might lead to significantly larger databases though.
• Store a file path in the database. But leading where? This would require additional user input.
• Generate previews on the fly through /rgb or /singleband with a low zoom level, or add another API endpoint that reads a whole dataset (as opposed to an XYZ tile).

[dionhaefner]

Should be very easy to implement, too. Passing bounds to the raster driver is already optional and defaults to reading the entire file. So we’d just have to register another flask route for the preview, and do some adjustments in the handler to make xyz optional.

[mrpgraae]

It automatically uses the appropriate overview, and we compute overviews in optimize-rasters until we are below TILE_SIZE, so everything should work out of the box.

Sweet! 👌