[Human App][Text Example] Integrate Text Example Job Type into Human App

[simulacrum6]

Description
The new job type for the text example (#778) needs to be integrated into the human app. This requires adding a registration function into the backend and requires a registration function, projects overview and password lookup on the frontend.

Implementation details

When users want to perform a text span annotation job, they

• need to be registered to the exchange oracle
• need to request assignment of an annotation task

Once they request an assignment, they will receive a password for this particular assignment (required by the annotation tool).

This means that the backend needs to send a request to the exchange oracle's /user/register endpoint (see #1350) to register the user and the /job/assign endpoint to assign a job (see the exchange oracle specification). The assign job endpoint will contains the password for the assigned task and a link to the annotation tool.

{ password: str, url: str }

Those need to be stored on the users's profile and displayed to the user in the frontend.