Update client-go to v1.19.7

[mikkeloscar]

Early spring cleaning of es-operator:

• Updates client-go to v1.19.7 (latest version running in Zalando clusters as of CW03)
• Introduces CRD generation from types.go file. Enhances the CRDs with better description and it will be easier to make changes in the future.

[otrosien]

E2E failing: The CustomResourceDefinition "elasticsearchdatasets.zalando.org" is invalid: spec.validation.openAPIV3Schema.properties[spec].properties[scaling].properties[diskUsagePercentScaledownWatermark].type: Required value: must not be empty for specified object fields

[mikkeloscar]

@otrosien This is because we were using float64 for the diskUsagePercentScaledownWatermark which is not supported by the CRD generation tooling and is generally not well supported or recommended in Kubernetes (Example of how floats are not stable because the precision: zalando-incubator/stackset-controller#214).

I have now changed the value to int32 as I believe there is no real value in being able to define percent with float precision. All examples already use whole integers for this value.

[otrosien]

apparently something changed for mandatory attributes.

[mikkeloscar]

@otrosien Great that we have this check to catch it :)

[mikkeloscar]

Correctly annotated the optional fields so they are optional in the CRD spec.

[mikkeloscar]

👍

[otrosien]

👍