feat(resmgr): cluster-blueprint family — REST client + host_config/host_role/host_config_assignment + blueprint DS

[PF9-pushkar]

Adds the first PCD-native (non-OpenStack) service to the provider, closing the cluster-blueprint gap from the api-docs audit.

New client pattern

resmgr has no gophercloud support, so clients.Config.ResmgrV2Client() is a hand-written REST client: it resolves the resmgr catalog endpoint via the ProviderClient's EndpointLocator and reuses the shared authenticated ProviderClient for tokens. Verified live against the CE lab.

Resources + data source

Type	API
pcd_host_config	CRUD /hostconfigs — traffic-type↔interface mapping + physical-network labels
pcd_host_role	PUT/DELETE /hosts/{id}/roles/{name} — assign a role (e.g. pf9-ostackhost-neutron); Read checks the host's roles
pcd_host_config_assignment	PUT/DELETE /hosts/{id}/hostconfig/{id}; Read checks host.hostconfig_id
pcd_cluster_blueprint (data source)	read a blueprint by name; storage_backends_json exposed as a sensitive JSON string (driver credentials)

Schema modelled on the live lab responses (probed read-only), which are richer than the api-docs.

Adversarial review — 2 fixed

Both the same class as the block-storage family (fragile post-write read-back), confirmed against framework source:

1. host_config Create could orphan the created object on a read-back failure → now seeds state from the POST response and warns.
2. host_config Update could leave stale state on a read-back failure → now persists the applied plan and warns.

Deliberately deferred: the pcd_cluster_blueprint resource

Its write path is uniquely risky — full-object PUT, storageBackends with plaintext credentials, and create semantics I can't safely verify without mutating the lab's one working blueprint. Own follow-up (see DECISIONS.md).

Testing

build / vet / gofmt / golangci-lint (0) / unit tests / terraform fmt / docs generate — all clean. Mutating acc tests are opt-in (PCD_ACC_RESMGR); the blueprint DS test reads an existing blueprint (PCD_ACC_BLUEPRINT_NAME).