Add documentation on Yaeger architecture

[meronbrouwer]

No description provided.

[sanmai-NL]

@meronbrouwer In time, let's do a brief hacking session together where we encode properties of the architecture as ArchUnit tests. This way, we can gain a common understanding and produce more valuable artifacts than hard-to-maintain documentation. Since ArchUnit tests are quite readable (for the target audience/stakeholders of software developers), these are as good as prose.

[meronbrouwer]

The documentation should reflect the way we expect our students to document their architecture. ArchUnit can be a nice supplement to this, but that should be addressed in a different issue.