Move sample messages to Rust test

[stappersg]

No description provided.

[stappersg]

Move sample messages to Rust test

In stead of cargo test .... should cargo run --example .... be used.
In #82 work in progress to achieve that.
Please consider to postpone to merge this MR.

[stappersg]

Closing this merge request:

• There original request of have clean commits is represented in many other merge request
• What this MR would add, is better provided in new file: backend/examples/crabfeeder.rs #82, Added CID email to samples #83 and new file: samples/normal.eml #84
• Getting this MR merged would require other merge requests slash commits to get it clean up