Improve error message "Can't find such service: microsoft"#50

At a first install attempt, I have deinstalled mailctl and installed oama. I have followed the first instruction. ```When you run oama at the first time it will create the initial config file what you need to edit.``` Source: https://github.com/pdobsan/oama/blob/main/README.md#configuration ``` arthur@z97:~$ oama WARNING -- Could not find config file: /home/arthur/.config/oama/config.yaml Creating initial config file ... Edit it then start oama again. ``` After which I have blindly copy/pasted the command from the config guide. ``` arthur@z97:~$ oama authorize microsoft [email protected] oama: Can't find such service: microsoft CallStack (from HasCallStack): error, called at lib/OAMa/Authorization.hs:410:16 in oama-0.11.1-inplace:OAMa.Authorization ``` I probably need to configure the config file, however, it would be nicer if a error message appears with a clearer description what to do and preferably without a call stack.