[operator] Document env vars for overriding Jaeger image sources

[orthoxerox]

This is important when running Jaeger on a self-hosted cluster with no direct access to the Docker Hub.

The support for them was added in jaegertracing/jaeger-operator#21, but neither the documentation nor the deployment YAML indicate they exist and what their names are. I had to look at the source code and read Viper documentation to learn that they should be called JAEGER-ALL-IN-ONE-IMAGE, OPENSHIFT-OAUTH-PROXY-IMAGE etc.

[jpkrohling]

How do you feel about sending a PR with your proposal? The appropriate place for that would be the documentation repository, here: https://github.com/jaegertracing/documentation/blob/master/content/docs/next-release/operator.md

For the record, you can see all the flags by running the image with the start command and --help flag:

$ docker run jaegertracing/jaeger-operator:1.14.0 start --help
Starts a new Jaeger Operator

Usage:
  jaeger-operator start [flags]

Flags:
      --es-provision string                      Whether to auto-provision an Elasticsearch cluster for suitable Jaeger instances. Possible values: 'yes', 'no', 'auto'. When set to 'auto' and the API name 'logging.openshift.io' is available, auto-provisioning is enabled. (default "auto")
  -h, --help                                     help for start
      --jaeger-agent-image string                The Docker image for the Jaeger Agent (default "jaegertracing/jaeger-agent")
      --jaeger-all-in-one-image string           The Docker image for the Jaeger all-in-one (default "jaegertracing/all-in-one")
      --jaeger-cassandra-schema-image string     The Docker image for the Jaeger Cassandra Schema (default "jaegertracing/jaeger-cassandra-schema")
      --jaeger-collector-image string            The Docker image for the Jaeger Collector (default "jaegertracing/jaeger-collector")
      --jaeger-es-index-cleaner-image string     The Docker image for the Jaeger Elasticsearch Index Cleaner (default "jaegertracing/jaeger-es-index-cleaner")
      --jaeger-es-rollover-image string          The Docker image for the Jaeger Elasticsearch Rollover (default "jaegertracing/jaeger-es-rollover")
      --jaeger-ingester-image string             The Docker image for the Jaeger Ingester (default "jaegertracing/jaeger-ingester")
      --jaeger-query-image string                The Docker image for the Jaeger Query (default "jaegertracing/jaeger-query")
      --jaeger-spark-dependencies-image string   The Docker image for the Spark Dependencies Job (default "jaegertracing/spark-dependencies")
      --jaeger-version string                    Deprecated: the Jaeger version is now managed entirely by the operator. This option is currently no-op. (default "1.14.0")
      --log-level string                         The log-level for the operator. Possible values: trace, debug, info, warning, error, fatal, panic (default "info")
      --metrics-host string                      The host to bind the metrics port (default "0.0.0.0")
      --metrics-port int32                       The metrics port (default 8383)
      --openshift-oauth-proxy-image string       The Docker image location definition for the OpenShift OAuth Proxy (default "openshift/oauth-proxy:latest")
      --platform string                          The target platform the operator will run. Possible values: 'kubernetes', 'openshift', 'auto-detect' (default "auto-detect")

Global Flags:
      --config string   config file (default is $HOME/.jaeger-operator.yaml)

[orthoxerox]

Sure, I'll make a PR for this. I just need to get to a machine with a git client so I can sign my commit.

[yurishkuro]

Signing a commit is just adding a plain text line at the end of the comment. You can look at other commits in this repo for examples.