figure out how to reject multiple `infra` type constructs at schema level when they are provided in their explicit form.

[3p3r]

Per MVP design docs, infra constructs (network, cluster, and cicd) can be either omitted from mu.yml or appear at most once. When provided in the shorthand version, this issue is automatically resolved due to the nature of json objects (two keys with the same name cannot coexist in the same object).

When provided in the explicit version, the following mu.yml should be rejected at the schema level:

mu:
  name1:
    type: cicd
    ...

  name2:
    type: cicd
    ...

[3p3r]

Closing this ticket per changes introduced to the schema in 41da5b08894713c9edfcb15a2b614771e9c1a934