Authorisation for access

[ashuchow]

Currently, the link for metabase manager is accessible to all, requires entering of credentials every time and storing json files (that store credentials) locally to execute established sync paths. Ease of use problems and security issues can become a problem.

I propose setting up authorisation to use the manager so we can have better security, tracking of which user syncronized across which source and destination, and also be able to save the metabase instance(s) credentials so that the user doesn't need to manually add a link and provide credentials for setting up the configuration for a sync.