extraConfigs

[itamar-marom]

Fixes #76
Fixes #75

Description

New field in the API:

// References to ConfigMaps holding more files to mount to the CommonConfigMountPath.
// +optional
ExtraCommonConfig []*v1.ObjectReference `json:"extraCommonConfig"`

Each ConfigMap can hold as many extra files as the user wants.
The operator will go over the ConfigMap object, then will fetch all file names (key) and their content (value) from the ConfigMaps. It will add them to the common ConfigMap that is being mounted into the _common directory.

Had to refactor e2e to work smoothly without unnecessary long sleep commands + Added an E2E test to check the new feature.

Option 1: Mounting files as subPath - not good enough:
Kubernetes documentation states, A container using a ConfigMap as a [subPath](https://kubernetes.io/docs/concepts/storage/volumes/#using-subpath) volume will not receive ConfigMap updates.

Options 2: the above solution

• Added a new field: ExtraCommonConfig
• Moved all configuration-related functions to configuration.go
• Created a new function called addExtraCommonConfig that is being called in makeCommonConfigMap

---

This PR has:

• been tested on a real K8S cluster to ensure creation of a brand new Druid cluster works.
• been tested for backward compatibility on a real K*S cluster by applying the changes introduced here on an existing Druid cluster. If there are any backward incompatible changes then they have been noted in the PR description.
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added documentation for new or modified features or behaviors.

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Key changed/added files in this PR

• configuration.go
• Druid API
• e2e

[AdheipSingh]

Lets not add methods now. This will need a big change on all the code structure. Not just configmaps.
Ideally we would want another interface as druidBuilder to expose this methods.

[itamar-marom]

Removed it from the Reconciler object. Will fix the e2e and ping you

[itamar-marom]

@AdheipSingh ready with no new methods for the reconcile object.
I do wish to discuss about refactoring as the controller becomes more and more complicated.

[itamar-marom]

Generally, with this feature, we can then eliminate all other "common" fields and rename this to commonConfig which will be built from other ConfigMaps.

[itamar-marom]

Just updated the new chart version since it includes updated crd

[AdheipSingh]

Thanks @itamar-marom . Merging it .