Reduce number of spans in django framework

[hmstepanek]

Overview

This removes the following middlewares from being instrumented in an effort to reduce the number of spans created when instrumenting django:

• CsrfViewMiddleware
• XFrameOptionsMiddleware
• MessageMiddleware
• CsrfViewMiddleware
• CommonMiddleware
• SecurityMiddleware

Related Github Issue

Spike DT Improvements

[github-actions]

🦙 MegaLinter status: ❌ ERROR

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ PYTHON	bandit	1		0	4.98s
✅ PYTHON	black	4	1	0	1.31s
✅ PYTHON	flake8	4		0	0.46s
✅ PYTHON	isort	4	1	0	0.21s
❌ PYTHON	pylint	4		27	3.9s

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[codecov-commenter]

Codecov Report

Merging #779 (97e16d2) into develop-dt-improvements (16a0b87) will increase coverage by 0.17%.
The diff coverage is 77.77%.

@@                     Coverage Diff                     @@
##           develop-dt-improvements     #779      +/-   ##
===========================================================
+ Coverage                    65.28%   65.46%   +0.17%     
===========================================================
  Files                           58       58              
  Lines                         6401     6396       -5     
  Branches                      1136     1136              
===========================================================
+ Hits                          4179     4187       +8     
+ Misses                        1895     1881      -14     
- Partials                       327      328       +1     

Impacted Files	Coverage Δ
newrelic/hooks/framework_django.py	75.82% <77.77%> (+3.63%)	⬆️

... and 1 file with indirect coverage changes

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[umaannamalai]

In situations like this in the agent, we would typically make this into a frozenset() for performance reasons.

[umaannamalai]

Is there an advantage to leaving the metrics in for the ignored middlewares with a count of None vs dropping them from the scoped metric list?

[hmstepanek]

I did this specifically to make sure they were dropped because if you simply don't look for them they could still be there but the test wouldn't catch it.

[umaannamalai]

Based on the warning listed for security middleware here, could it be worth it to keep the SecurityMiddleware spans around to support potential future vulnerability detection?

[hmstepanek]

That's good point. Since this middleware just sets security related headers, for vuln detection I imagine we would want to capture those headers. I don't think we would specifically need to hook into this middleware to capture the security related headers though unless I'm missing something. You should be able to capture these headers on the response request independent of wrapping this particular middleware.

[umaannamalai]

Looks great!