Conform query parameters to JSON:API specs

[edan-bainglass]

This PR aligns query parameters with JSON:API specs. See README.md for details.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 93.16239% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.24%. Comparing base (2c174ed) to head (217c963).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
aiida_restapi/common/query.py	91.48%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #157      +/-   ##
==========================================
+ Coverage   89.09%   89.24%   +0.14%     
==========================================
  Files          50       50              
  Lines        2036     2110      +74     
==========================================
+ Hits         1814     1883      +69     
- Misses        222      227       +5     

Flag	Coverage Δ
pytests	89.24% <93.16%> (+0.14%)	⬆️

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[edan-bainglass]

@Bud-Macaulay a few things:

1. Don't mind the failing test. That's due to a recent aiida-core change to be addressed shortly - see #7507 degrades the Pydantic model system 🥲 aiida-core#7508
2. It remains to be decided if such a "sophisticated" query parameter system is needed in light of the QE endpoint (and a stable GraphQL endpoint), though I would argue JSON:API-based query params are still a nice shortcut
3. Have a look at how I construct pagination links w.r.t existing query params at the bottom of this file. I may be overthinking it, but without the safe characters, pagination links looked like a string of % signs 🥲 Not so friendly, but maybe this stuff is not for humans to read anyhow. Second opinion 🙏
4. In the current state, we have the following validations:
   a. DB validation for field names at the router entity level (e.g., pinging the /nodes endpoint with filter[metadata] will naturally raise a validation error - metadata is not a field of nodes), but attributes.whatever is not validated, nor is it in the QueryBuilder itself!
   b. Operator validation is done against a set of allowed operations, but we do not validate if the operator is valid for the field, nor does the QueryBuilder!