Add ability to configure additional network interface names in image meta

[Mierdin]

The networkInterfaces field in the image metadata was created long ago, but currently does nothing. The idea at the time was to use this purely as a descriptive field, so that lesson authors could know which network interfaces to expect a given image to use.

However, Multus gives the ability to configure interface names when attaching pods to a network, so we can go beyond simply describing defaults - we can use this as a way of overriding those defaults, and set interface names at attachment time. This makes it possible to accommodate images that expect certain interface names, as described in nre-learning/nrelabs-curriculum#339

The field is now optional, but when present, will be used to specify the name of all interfaces following eth0, and will be consumed in order of the networks a pod is attached to.

[codecov]

Codecov Report

Merging #214 (3ab22c8) into master (ad4b25a) will increase coverage by 1.63%.
The diff coverage is 73.68%.

@@            Coverage Diff             @@
##           master     #214      +/-   ##
==========================================
+ Coverage   28.54%   30.17%   +1.63%     
==========================================
  Files          24       24              
  Lines        2032     2184     +152     
==========================================
+ Hits          580      659      +79     
- Misses       1402     1469      +67     
- Partials       50       56       +6     

Impacted Files	Coverage Δ
db/ingestors/images.go	69.56% <66.66%> (+1.99%)	⬆️
scheduler/backends/kubernetes/pods.go	48.42% <76.92%> (+1.86%)	⬆️
config/config.go	74.00% <0.00%> (-1.56%)	⬇️
scheduler/backends/kubernetes/jobs.go	23.42% <0.00%> (-0.67%)	⬇️
scheduler/backends/kubernetes/kubernetes.go	15.85% <0.00%> (-0.50%)	⬇️
db/db.go	0.00% <0.00%> (ø)
api/exp/server.go	0.00% <0.00%> (ø)
services/utils.go	0.00% <0.00%> (ø)
api/exp/lessons.go	0.00% <0.00%> (ø)
api/exp/curricula.go	0.00% <0.00%> (ø)
... and 16 more

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[hellt]

Hi @Mierdin
do you want me to test this? Or is it not ready yet?

[Mierdin]

@hellt No, this should be okay, just needed to cross some Ts. I'll let you know in the curriculum discussion when you should be ready to open a PR.