fix: trino thread app missing full context

[dpgaspar]

SUMMARY

Fixes the issue where Trino SQL execution was missing Flask's g values in the context.
Flask's requests and g are local to the request thread or greenlet, by creating a new thread we loose this context.

This PR passes a copy of g into the thread, g is then recreated inside the thread, this g will be local to the thread but will contain all the necessary context of the current flask request

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.64%. Comparing base (76d897e) to head (6ed299d).
Report is 1094 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #29981       +/-   ##
===========================================
+ Coverage   60.48%   83.64%   +23.16%     
===========================================
  Files        1931      528     -1403     
  Lines       76236    38150    -38086     
  Branches     8568        0     -8568     
===========================================
- Hits        46114    31912    -14202     
+ Misses      28017     6238    -21779     
+ Partials     2105        0     -2105     

Flag	Coverage Δ
hive	48.95% <33.33%> (-0.22%)	⬇️
javascript	?
mysql	76.64% <33.33%> (?)
postgres	76.73% <33.33%> (?)
presto	53.50% <33.33%> (-0.31%)	⬇️
python	83.64% <100.00%> (+20.16%)	⬆️
sqlite	76.22% <33.33%> (?)
unit	60.31% <100.00%> (+2.68%)	⬆️

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[michael-s-molina]

@dpgaspar I did a quick GPT search.

from flask import current_app
import threading

def my_thread():
    with current_app.app_context():
        # Access Flask context within the thread
        app = current_app._get_current_object()
        # Do something with the app

# Create and start the thread
thread = threading.Thread(target=my_thread)
thread.start()

Would something like this work for our use cases?

[dpgaspar]

seems basically similar, except I'm passing the current_app into the thread, also we need to recreate g inside the thread

[michael-s-molina]

Can't we use copy_current_request_context?

@copy_current_request_context
def worker():
    # Access Flask's g object here
    # Your code goes here

[dpgaspar]

only the request context is copied according to: pallets/flask#3306

[joaoferrao]

Indeed not including @ copy_current_request_context makes the thread's downstream calls url_for function calls fail with the screenshot here #27631 (comment)

I found this out in the context adapting #27631 for Trino. My understanding is that, when using OAuth2 config, the class OAuth2ClientConfigSchema will be called in a separated thread and has this missing information.

[dpgaspar]

Thank you for the review @michael-s-molina