Implement discussion features + stop fallthrough

[BitcoinMitchell]

Description

Shows the BTCPay fallback rate provider status on configure page, including a warning if none is set. I've improved the log levels and added a section to the README about making sure to enable Logs by email.

Also contains a quick fix to prevent a fall through in the WebhookHandler.

In my store

• Fixes Email store owner when the module runs into an error #222
• Fixes Show the store owner if they have a fallback rate set #221
• Fixes Email store owner when the module performs a reset #187

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change which improves the codebase)

How Has This Been Tested?

Ran it on my local development setup (which I will commit in the next PR).

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have checked my code and corrected any misspellings