Upload and Download dumps

[ManyTheFish]

Summary

Add a route that allows the download of a dump stored in the server.

Motivations

meilisearch/meilisearch#1006 (comment)

Explanation

download a dump:
GET: /dumps/:dump_uid
200: stream of the file

upload a dump:
POST?: /dumps/:dump_uid

Implementation

Download:

• using an HttpResponse streaming ?
• use actix file services ?

Upload:

• https://turreta.com/2019/09/26/rust-upload-files-in-actix-web/ ?
• https://docs.rs/actix-multipart/0.3.0/actix_multipart/ ?

[ppamorim]

@LegendreM I wrote down some of my thoughts about this feature.

• I agree with the routes GET - /dumps/:dump_uid and POST - /dumps/:dump_uid, but I think the route POST - /dumps should be renamed to POST - /dumps/create to prevent any confusion with GET - /dumps/:dump_uid.

• I believe that by using HttpResponse for both download and upload functions are essential to keep the API stable, by dividing the download function to services and HttpResponse to the upload can be confusing for the user. If we use services the user will need to manually find the dump in the services folder instead of simply requesting the dump file. Also, this limits us for new implementation and additional features related to the download of dumps.

Some information:

• I already implemented the download function with the help from @MarinPostma.
• I started the development of the uploader but I could not find a relatively easy way to make everything non-blocking by using actix + tokio and supporting multipart upload at the same time.