Materials Cloud implementation: index metadatabase & other updates

[eimrek]

Added

• Optimade index meta-database
• Saving the metadata of each entry in the mongodb
• Using the metadata in the index and the landing page.

Running at https://dev-optimade.materialscloud.org/

Additonally, an important point:

I separated data injection and starting of the containers. The reasoning is the following:

The initial two steps:

1. download from archive;
2. conversion to jsonl;

are just needed for setting up the MongoDB. If the mongodb is there, these two steps are not needed. Therefore, it makes sense to have this be indepedent from running the docker containers. This makes stopping and re-running the containers (e.g. if i want to test a new docker image) more convenient, if data injection is decoupled. Possibly, i would even suggest to move the data_inject function from optimade-launch to mc_optimade.

Pinging @ml-evs @unkcpz, just to be aware of the last point.

[eimrek]

These changes shouldn't conflict with other parts so I'll just merge