[Feature Request] Support regulated and non-regulated multi-tenancy within a single GCP Organization #388

Feature Description

Enable Stellar Engine (fast/stages-aw/*) to support isolated multi-tenancy across regulated and non-regulated environments within a single Google Cloud Organization, without requiring separate Google Cloud Organizations per compliance tier.

Use Case

Many public-sector, higher-education, and research institutions operate under a single centralized Google Cloud Organization (bound to one primary identity domain) while running both regulated and non-regulated workloads side by side:

1. Regulated workloads requiring Assured Workloads compliance enclaves and strict guardrails (e.g., HIPAA, FedRAMP Moderate/High, or DoD IL4/IL5 with mandatory CMEK, regional restrictions, and dedicated Shared VPC boundary inspection).
2. Non-regulated workloads (e.g., general academic research, open collaboration, or multi-region burst HPC/AI compute) where organization-wide Assured Workloads constraints, single-region lock-in, or mandatory CMEK introduce unnecessary operational friction and cost.

Today, Stellar Engine assumes a centralized, single-regime Organization deployment:

• 0-bootstrap binds directly to the root organization (setIAM.sh, organization-level log_sinks, and org_policies_config) and configures a single global assured_workloads regime and location.
• 1-resman provisions tenants that all inherit the same centralized Stage 0 and Stage 2 compliance controls and network perimeter.
• 3-security enforces uniform security constraints (such as gcp.restrictNonCmekServices and gcp.restrictCmekCryptoKeyProjects).

Because of this coupling, adopting Stellar Engine for an organization with both HIPAA/regulated and non-regulated workloads currently forces deploying two separate Google Cloud Organizations or bypassing Stellar Engine in favor of upstream Cloud Foundation Fabric (FAST).

Proposed Solution

Support mixed-compliance multi-tenancy within a single Google Cloud Organization via one or both of the following patterns:

1. Folder-Scoped (Sub-Org Enclave) Deployment Mode:
   • Allow 0-bootstrap and downstream stages (1-resman, 2-networking-*, 3-security) to target a designated parent Folder ID rather than requiring exclusive root Organization ownership, enabling one or more regulated Stellar Engine enclaves to coexist alongside non-regulated folders/FAST stages within the same Organization.
2. Per-Tenant / Per-Enclave Compliance Tiers in 1-resman, 2-networking, and 3-security:
   • Allow tenants (or tenant groups/folders) in 1-resman to specify distinct compliance profiles—provisioning Assured Workloads folders (e.g., HIPAA, FedRAMP Moderate/High, IL4/IL5) and scoped Organization Policies, Shared VPCs, and CMEK enforcement only on regulated tenant hierarchies while allowing non-regulated tenant folders under the same Stage 0 administrative foundation.

Compliance & Deployment Context

• Target Deployment Type(s):
  • US Region Restricted (e.g., Access Policy constraint)
  • FedRAMP Moderate
  • FedRAMP High
  • DoD IL4
  • DoD IL5
  • All / General (including mixed HIPAA / Assured Workloads + non-regulated multi-tenant organizations)
• Relevant NIST 800-53r5 Controls: AC-3 (Access Enforcement), AC-4 (Information Flow Enforcement), AC-6 (Least Privilege), SC-7 (Boundary Protection), CM-2 (Baseline Configuration) — scoping strict enclave controls to regulated tenant boundaries without over-constraining non-regulated tenants in the same GCP Organization.

Reusability Check

Stellar Engine prioritizes reusability.

• I have checked if this functionality can be achieved by extending an existing module or blueprint.
• I have verified that this does not duplicate existing functionality.

Alternatives Considered

1. Two separate Google Cloud Organizations: Standing up one Stellar Engine GCP Organization for regulated (e.g., HIPAA) workloads and a second GCP Organization for non-regulated workloads. This duplicates Cloud Identity/SSO federation, billing administration, and platform operations.
2. Using upstream Cloud Foundation Fabric (FAST) directly: Deploying standard FAST at the organization root and manually creating Assured Workloads folders for regulated workloads. While this supports mixed-tenancy in one organization, adopters lose Stellar Engine's turnkey stages-aw compliance automation and pre-mapped NIST SP 800-53r5 ATO artifacts.

Additional Context

Supporting coexisting regulated and non-regulated tenants within a single Google Cloud Organization aligns Stellar Engine with upstream Cloud Foundation Fabric (FAST) architectural flexibility while preserving Stellar Engine's ATO acceleration for regulated enclaves.