Session HTTP + Websocket URLs

[nokome]

Previously only a Websocket URL was exposed for session job. This PR also exposes a HTTP URL as well.

The API for jobs has changed so that each job has a urls property which maps the protocol to the URL. This is similar to Executa's interface for the addresses property of a executor's manifest. Perhaps this property should be called addresses for consistency and client compatibility?

In either case, for backwards compatibility the url property is retained and points to the Websocket URL.

This needs some further testing before merging.

[codecov]

Codecov Report

Merging #798 into master will decrease coverage by 0.08%.
The diff coverage is 42.55%.

@@            Coverage Diff             @@
##           master     #798      +/-   ##
==========================================
- Coverage   66.51%   66.42%   -0.09%     
==========================================
  Files         107      107              
  Lines        5981     6002      +21     
==========================================
+ Hits         3978     3987       +9     
- Misses       2003     2015      +12     

Impacted Files	Coverage Δ
manager/jobs/api/views.py	57.07% <0.00%> (-2.24%)	⬇️
worker/jobs/session/kubernetes_session.py	22.04% <0.00%> (ø)
worker/jobs/session/subprocess_session.py	0.00% <0.00%> (ø)
manager/jobs/api/serializers.py	87.20% <46.15%> (-0.45%)	⬇️
worker/jobs/pin.py	90.00% <71.42%> (-4.24%)	⬇️
manager/jobs/models.py	66.11% <100.00%> (ø)
manager/manager/settings.py	95.89% <100.00%> (ø)
manager/manager/version.py	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0d74f7f...2142da3. Read the comment docs.