Accomodate pubMLST authentication change

[Vince-janv]

Description

According to this information the pubMLST database will require users to authenticate themselves to perform any type of requests (even GETs).

In microSALT/utils/referencer.py microSALT fetches stuff from there. This is performed on the first micro-analysis run every day.

Not authenticating will result in not being able to fetch recent data

API docs: https://bigsdb.readthedocs.io/en/latest/rest.html#api-oauth

[Vince-janv]

Technical refinement:

• Use prod-user to authenticate
• Use credentials to authenticate the requests