[FEATURE] KymaEnvironment Schema Validation

[sdischer-sap]

Is your feature request related to a problem?

We recently see more problems (e.g. #104) with the fact that the KymaEnvironment parameters schemaless. This together with a recent change in the Provisioning API leads to a potential continous update loop due to a continous drift detection of ignored fields in the Kyma side. This is particularily bad, since the Kyma side will eventually fail the updates and bring the instance into a failure state after too many update requests.

Describe the solution you'd like

A potential solution to this might be adding some dynamic runtime validation of schema based on the createSchema and updateSchema fields of the API (see https://api.sap.com/api/APIProvisioningService/path/getAvailableEnvironments). We can use those to filter out attributes that are only relevant for updates and return an error if there are attributes entirely unknown to the schema.
This would hopefully solve those continous update issues currently see.

Potential alternatives

Apart from making those semantic checks it makes sense to add a circuit breaker. This will be dealt with in this issue:
#164

Acceptance criteria:

• Controller returns error in case of schema contains unknown attributes (according to create- and updateschema)
• Controller filters out attributes that are only part of the createschema to send a payload valid according to the updateschema
• stretch/thought: utilize this logic in the drift detection step
• implement as intializer function to easily be reusable by other components

Additional context

• Schema Docs
• Guide on schema validation