Invert unions during manifest generation

[ronenh]

This results in the expected structure for unions:

  ### display_name: Tenant ###
  tenant:
    relations:
      ### display_name: tenant:account ###
      account: user
      ### display_name: tenant:owner ###
      owner: group
      ### display_name: tenant:admin ###
      admin: owner | group
      ### display_name: tenant:member ###
      member: owner | admin | group
      ### display_name: tenant:viewer ###
      viewer: owner | admin | member | group
      ### display_name: tenant:decision-log-reader ###
      decision-log-reader: group
      ### display_name: tenant:discovery-client ###
      discovery-client: group
      ### display_name: tenant:edge-authorizer ###
      edge-authorizer: group
      ### display_name: tenant:directory-client-reader ###
      directory-client-reader: directory-client-writer | group
      ### display_name: tenant:directory-client-writer ###
      directory-client-writer: group

[github-actions]

Pull Request Test Coverage Report for Build 6671672253

• 0 of 19 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.8%) to 50.579%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
migrate/migrate.go	0	19	0.0%

Totals
Change from base Build 6669118115:	-0.8%
Covered Lines:	611
Relevant Lines:	1208

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💛 - Coveralls