- Bump .Net framework to 4.8
- Fix build errors after import into VS 2022

Refers to #20

Refers to #20

Refers to #35

Placed in namespace ATxCommon.Monitoring, using its own timer to update
the values.

Refers to #36

The shared approach results in conflicts if the generated class is used
in ATxCommon which is imported in the other projects. This way we can
use the symbols defined via ATxCommon in all depending projects.

The downside is that it slows down the build-process a bit as every
build from a project depending on ATxCommon (read: all others) will
change the generated code and thus force a re-build of ATxCommon and
the project itself. Since building the entire solution is still just
a matter of seconds, that's a fair trade-off.

All projects (and namespaces) should start with an "ATx" prefix, having
a capital "AT" and a lowercase "x".

To avoid flooding recipients and / or SMTP servers.

Refers to #3, #4

Currently this is almost entirely untested and configuration for email
notifications is yet to be done.

Refers to #3

Since we have more to share between the applications than just the XML
wrappers, this is the location to keep common classes and methods.

Note that this only adds the new class library, it does not yet adjust
the existing service code to use it!

Refers to #21