Add OpenTracing configurability for APIcast environments

[miguelsorianod]

This exposes OpenTracing functionality provided by APIcast into the APIManager CR for the APIcast staging and production environments.

Design

New spec.apicast.stagingSpec.openTracing and spec.apicast.produtionSpec.openTracing sections have been added in the APIManager CR.

An example:

spec:
  apicast:
    stagingSpec:
      ...
      openTracing:
        enabled: true
        tracingLibrary: jaeger
        tracingConfigRef:
          name: mysecretname
    productionSpec:
       ...
      openTracing:
        enabled: true
        tracingLibrary: jaeger
        tracingConfigRef:
          name: mysecretname
  ...

• All attributes in the openTracing section are optional
• If the enabled flag is not specified, it defaults to false
• If the tracingLibrary flag is not specified, it defaults to jaeger
• If the tracingConfigRef flag is not specified, it defaults to a default tracing configuration specific to the set tracingLirary. This default tracing configuration is provided in the APIcast image itself

The configuration is mounted into the APIcast pod by looking at a config key in the provided secret name and mounted in /opt/app-root/src/tracing-configs/tracing-config-<tracing_library_name>-<secret_name>, for example in opt/app-root/src/tracing-configs/tracing-config-jaeger-mysecretname

The volume tracking annotation mechanism has been implemented for the opentracing-related Volumes in APIcast DeploymentConfigs in order to reconcile addition/removal of them without altering manually mounted ones.

The annotation format for them is:

apps.3scale.net/tracing-config-volume-<md5sum-of-volume-name>: <volume-name>

The Volume name format is:

tracing-config-<tracing_library>-<tracing_config_secret_name>

[eguzki]

Overall looking good. I dropped some comments

[eguzki]

Some doc about how to see opentracing result when enabled?

[miguelsorianod]

Some doc about how to see opentracing result when enabled?

That depends on how they install opentracing. They should see the traces in the opentracing ui if successfully working

[codeclimate]

Code Climate has analyzed commit bd50bdc and detected 24 issues on this pull request.

Here's the issue category breakdown:

Category	Count
Complexity	5
Duplication	12
Style	7

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