Business Account - refine AccountService

Should serve as a good example for future services that wrap other API integrations.
- add __init__ method
- decouple from flask app context (no current_app, etc. - could give option for passing in flask app?)
- sets passed in config (urls, secrets)
- sets logger
- consider setting a passed in 'flags'
- add centralized method for calling the api its wrapping
- Example: https://github.com/bcgov/registries-search/blob/main/search-api/src/search_api/services/authz.py#L49
- add in caching (NOT flask caching as we want the option to use this class without a flask app)
- fill out test suite / rework tests setup