Add handling of unsupported HTTP methods inside adapter

[sshishov]

Add handling of unsupported HTTP methods inside adapter

Background

We are using Kubernetes in our setup and Istio Gateway which is using Envoy behind the scenes.

• Unfortunately, envoy does not support custom HTTP methods, according to the issue.
• When this issue will be closed, the parser will allow custom HTTP verbs but currently, we are locked out.

The only way to have a workaround, to replace list custom verb with get plus additional params.

NOTE

Additional actions:

• now we can always use LIST everywhere and if the adapter does not support it, it will be converted before the request.
• there are a lot of places with logic if method == 'LIST' etc... And there are a lot of places where we are propagating list=true to params.

Fixes #551

[sshishov]

If needed, I can try to update the code everywhere where this addition of list=true is used.
I just do not know if every endpoint which is using it supports LIST method of HTTP.
If not, then this inconsistency should be fixed, imho.

[codecov]

Codecov Report

Merging #689 (cac5e71) into develop (c1a88fe) will decrease coverage by 0.11%.
The diff coverage is 28.57%.

@@             Coverage Diff             @@
##           develop     #689      +/-   ##
===========================================
- Coverage    83.76%   83.64%   -0.12%     
===========================================
  Files           61       61              
  Lines         3216     3223       +7     
===========================================
+ Hits          2694     2696       +2     
- Misses         522      527       +5     

Impacted Files	Coverage Δ
hvac/adapters.py	85.56% <28.57%> (-4.44%)	⬇️