Add handling of environment variables from ConfigMaps and Secrets

[oldium]

Description:

Added detection and reading of environment variables defined in PODs resources like ConfigMaps and Secrets. Supports both envFrom and valueFrom forms.

Link to tracking Issue(s):

• Resolves:
  • NodeJS Auto instrumentation overrides NODE_OPTIONS when defined from ConfigMap #1393
  • Setting JAVA_TOOL_OPTIONS via configmap is not possible (replaced,ignored) #1814

Testing:

Added kubebuilder tests for new code, tested by deploying the generated image to OpenShift cluster.

Documentation:

This is an enhancement, which can be read also as a bug fix (missing feature), so I have not added any documentation.

Implementation notes/questions:

1. The ConfigMap support is in first commit, the Secret support is in the second commit. They work the same, they both support “if exists” checks and are able to extend the existing value (append) into a newly created (or updated) environment variable.
2. I was not sure about the Container class naming (or have some common methods prefix?), so please suggest how the main class/file should be named - I can change it easily. The class handles everything regarding environment variables on the container currently.
3. I was not sure about the usage of namespace name. The sdkInjector.inject method gets one in arguments, but Apache and Nginx auto-instrumentations are ignoring it and taking namespace name from POD definition or from PODs resource map, which looks wrong (at minimum this is suspicious). I took the namespace name from the POD and if not found, I fall back to the one supplied as a parameter to inject method.
4. I was not sure about the reading of Secrets (second commit) - whether it is secure to handle them fully. The implementation is as full as for ConfigMaps, so the values can be detected (“if exists” checks) and extended (“append when exists”) into a new or updated environment variable (so Secret is converted to env var!). If necessary, I can change the implementation to just recognise them (record the existence) but fail when the value should be extended.