TODOs of Composable

[roytman]

This issue contains different "TODO" tasks for the project. In the future, we might separate the issue to different tasks.

Functional Requirements

• Support "wait for" resource, wait until the checking recourse achieves the predefined state "Online", "Running" ...
• Support dynamic updates of values, define fields that cannot be updated.
• Support for an optional filed, if value of an optional filed cannot resolved during startup, the destination resource will be created without filed or with a default value, and can be updated later.
• Support group of checking resources
• Support label selector instead of name of input object
• Separate Composable Status as a sub-resource
• Support Update of existing underlying objects (resolve special use cases)
• Run Composable as non-privileged user
• Support multiple underlying objects
• Support values encryption and decryption.
• Support integration with HashiCorp Vault
• Support values concatenation.
• Support if - if else - else roles

None Functional Requirements

• Replace standard Golang logger, by a more leveled one. Suggestions: uber-go/zap and k8s.io/klog, k8s.io/apiserver/pkg/util/logs.
• Code Clean-up
• Add unit and e2e tests
• Prevent repeatable get resource calls for the same resource.
• Integrate travis workflow