Add a mini-language parser for generic GQL list filtering

[Jaymel]

Defined a method to change the query statement to sql statement.

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #305 into master will increase coverage by 1.15%.
The diff coverage is 88.00%.

@@            Coverage Diff             @@
##           master     #305      +/-   ##
==========================================
+ Coverage   49.42%   50.57%   +1.15%     
==========================================
  Files          42       46       +4     
  Lines        6503     7786    +1283     
==========================================
+ Hits         3214     3938     +724     
- Misses       3289     3848     +559     

Impacted Files	Coverage Δ
.../ai/backend/manager/models/minilang/queryfilter.py	88.00% <88.00%> (ø)
src/ai/backend/manager/models/domain.py	62.25% <0.00%> (-5.02%)	⬇️
src/ai/backend/gateway/auth.py	50.00% <0.00%> (-4.42%)	⬇️
src/ai/backend/manager/models/user.py	34.65% <0.00%> (-0.17%)	⬇️
src/ai/backend/manager/plugin/exceptions.py	100.00% <0.00%> (ø)
src/ai/backend/manager/exceptions.py	100.00% <0.00%> (ø)
src/ai/backend/manager/plugin/error_monitor.py	50.00% <0.00%> (ø)
src/ai/backend/gateway/exceptions.py	88.03% <0.00%> (+0.47%)	⬆️
src/ai/backend/manager/models/group.py	49.22% <0.00%> (+2.13%)	⬆️
... and 5 more

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[achimnol]

While I'm reviewing, please sign up the CLA and fix up the style issues indicated by lint checkers.

[achimnol]

Please check out the comments.
Also, where are the code changes for GQL list queries in other modules of ai.backend.manager.models?

[achimnol]

Overall, LGTM about fulfilling my functional requirements.
Since your internship has finished, I will do some style/code clean up.

[achimnol]

Now we need to use ai.backend.manager.models.minilang.queryfilter.QueryFilterParser in all paginated list GQL query resolver functions under ai.backend.manager.models, adding an optional string-type "filter" argument to all such queries.

[achimnol]

I will file a new issue for the application of QueryFilterParser, after merging this.