task wise mbtile generation

[Sujanadh]

fixes #890
this changes allows to generate the mbtiles of individual task using their task_id. if task_id is not provided it will generate the mbtiles of entire project boundary.

[spwoodcock]

For this to work we would also need to update the frontend.

But please also see the comments in the linked issue & how Rob proposed we solve this.
We still want to generate the tiles for the entire project, then subdivide.
I proposed a way to do this with project level PMTiles, then dividing into task level MBTiles on request.

I will probably make a PR for this in the coming weeks.

[Sujanadh]

so the tile of entire project must be generated not the task wise? and allowing to download tile of required task from the generated tile of entire project?

[spwoodcock]

Yes exactly.

osm-fieldwork does support outputting PMTiles, so we should do that.
The subdivision from PMTiles into MBTiles won't be simple though & will require delving into the format internals.

If you want to have a go, feel free, otherwise I will be working on this soon.

[spwoodcock]

Rob already gave his feedback for how to solve this: #890 (comment)

But he can always weigh in again.