📚 Improve schema docs

[ubmarco]

• More structure / headlines
• Document network recursion limit
• More explanation how to learn from tests
• Section that explains the basic schemas structure
• Primary field typing and relation to schemas.json

Fixes #1542 and #1539.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.95%. Comparing base (4e10030) to head (c1051a7).
⚠️ Report is 184 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1554      +/-   ##
==========================================
+ Coverage   86.87%   87.95%   +1.07%     
==========================================
  Files          56       70      +14     
  Lines        6532     9606    +3074     
==========================================
+ Hits         5675     8449    +2774     
- Misses        857     1157     +300     

Flag	Coverage Δ
pytests	87.95% <ø> (+1.07%)	⬆️

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[ubmarco]

@MrChocolateMoose I'd appreciate your feedback on the PR.

[chrisjsewell]

From a quick scan through, looks all good

[MrChocolateMoose]

I started reviewing this AM, but should be finished by the end of my day.

[ubmarco]

Thanks. Will wait with the merge until tomorrow.

[MrChocolateMoose]

I looked at the rendered docs and it looks good to me as well. It addresses my checklist of points I wrote.

I had a few side points that depending on the answer could warrant updates to the schema docs (e.g. some confusion on why I would set an enum value on the need field and as a validation schema, no mention of global regex options being disallowed). #1543 and #1536

No need to hold the PR up though. I approve.