Implementing Middlewares

[PizieDust]

This PR introduces continues the work on authentication. It introduces Middlewares, and a first middleware for authentication.

cc @hannesm

[hannesm]

it is not clear to me what the to_string does, we want to ensure that the "email" thingy is a `String -- so in the end I guess we need a json_utils module (since we've already similar code in user_model and albatross_json...

[hannesm]

overall looks great (on my mobile phone), do we need to check the expiration of the cookie somewhere? (fine to put this as todo, but I think we need to encode the timestamp when the cookie was issued to compare now - expiration_duration < issuing_timestamp.

I have no idea why the ocamlformat CI errored.

[PizieDust]

overall looks great (on my mobile phone), do we need to check the expiration of the cookie somewhere? (fine to put this as todo, but I think we need to encode the timestamp when the cookie was issued to compare now - expiration_duration < issuing_timestamp.

I have no idea why the ocamlformat CI errored.

Thank you for the review. These are very helpful.
Indeed we will need to add timestamps.

[hannesm]

thanks, merged. subsequent changes can follow in new prs