Allow regex for label keys

[deusxanima]

What

Would like to be able to use regex to match keys in RBAC label configs to allow for easier scalability in certain environments.

Example:

node_labels:
      'project-code': 'elmo'
      'project-label': 'elmo'

would become

    node_labels:
      '^project-(.*)$'': 'elmo'

Why

Customer ask to help with scalability

gz#4008

[russjones]

node_labels:
   service: '^project-(.*)$''
   service-type: '^project-(.*)$''

[zmb3]

The proposal is to support a syntax like the following:

contains(labels_matching(labels, "^project-.*$"), "elmo")

[russjones]

@jdconti Take a look at the above and tell us if this works for you?

[nklaassen]

This is addressed by label expressions released in 13.1.1

For example you can now write:

node_labels_expression: |
  contains(labels_matching("^project-(code|label)$"), "elmo")