improve instructions on how to use lsaai-mock

[MalinAhlberg]

Please describe the feature
As a user, I want good documentation so that can easily try storage-and-interfaces with lsaai-mock.

Acceptance criteria

• Instructions added on how to get a token from lsaa-mock
• instructions on how to get a visa
• instructions on how to upload files

Additional context

1. To get a token, you can open the URL http://localhost:8085/oidc in a web browser and then click the Login button. After successful login, you will enter a page with token, visa and a link to download the s3cmd config file.
2. To use the s3cmd.conf file for uploading and ingesting data, one need to change the entry use_https in the config file to False

Estimation of size: small/medium/big

Estimation of priority: low/medium/high

[aaperis]

• the visa part of ls-aai mock needs to be configured first
• add also instructions on how to download encrypted files from download