wip: MQL support for subscriptions

[ayirr7]

Legal Boilerplate

Look, I get it. The entity doing business as "Sentry" was incorporated in the State of Delaware in 2015 as Functional Software, Inc. and is gonna need some rights from me in order to utilize my contributions in this here PR. So here's the deal: I retain all rights, title and interest in and to my contributions, and by keeping this boilerplate intact I confirm that Sentry can use, modify, copy, and redistribute my contributions, under Sentry's choice of terms.

[sentry-io]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: src/sentry/snuba/tasks.py

Function	Unhandled Issue
_create_in_snuba	SnubaError: HTTP 500 response from Snuba! sentry.... Event Count: 2

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[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 78.12%. Comparing base (7b458d4) to head (1e6f348).
Report is 788 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #73808   +/-   ##
=======================================
  Coverage   78.11%   78.12%           
=======================================
  Files        6658     6658           
  Lines      297837   297839    +2     
  Branches    51239    51240    +1     
=======================================
+ Hits       232664   232673    +9     
+ Misses      58885    58877    -8     
- Partials     6288     6289    +1     

Files	Coverage Δ
src/sentry/snuba/tasks.py	92.17% <33.33%> (-1.64%)	⬇️

... and 5 files with indirect coverage changes

[getsantry]

This pull request has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you add the label WIP, I will leave it alone unless WIP is removed ... forever!

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"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀