Support specifying additional containers for OpenTelemetryCollector podspec

[diurnalist]

The primary motivation for this request is to add additional sidecars to the otel-collector pods that are controlled by the operator.

One use-case is for if you want to tell the collector to export to a sidecar that acts as an authenticated proxy (in case the ability to specify static headers in the otel-collector otlp export config is insufficient.) I'm sure there are other use cases that would apply in the future.

The Prometheus operator has support for a containers field in the spec, which allows adding or even overriding base container definitions. I'm not sure we have to go as far as that, but having some sort of additionalContainers would be nice. For completeness, initContainers support may also be helpful for supporting different flavors of deployment environment.

[initharrington]

I came here from open-telemetry/opentelemetry-helm-charts#650

I am trying to use file_storage extension and the operator.

I get a permission issue on start up:

2023-05-16T14:30:51.451Z	info	extensions/extensions.go:55	Stopping extensions...
2023-05-16T14:30:51.451Z	info	service/service.go:180	Shutdown complete.
Error: cannot start pipelines: open /var/lib/storage/otc/exporter_sumologic__logs: permission denied
2023/05/16 14:30:51 collector server run finished with error: cannot start pipelines: open /var/lib/storage/otc/exporter_sumologic__logs: permission denied

I cannot follow the initContainer workaround using the operator.

[diurnalist]

#1870 only adds support for init containers, not additional containers that run alongside the main pod container.