chore: remove dead code left over from pre-external-users custodial model

[salindne]

Background

When external parties + interactive submission landed (commits 766f169, 2397a44, e00a981), the older internal-party custodial registration model was retired. Several methods on the cantonsdk identity client and one config field were left behind with no remaining production callers.

This issue lists the orphans I could verify, with the rigor needed to remove them safely. It's a cleanup ticket — no behavioral change, just deleting dead code.

Confirmed dead code

1. Client.GrantActAsParty — fully dead

File: pkg/cantonsdk/identity/client.go — interface decl line 40, implementation lines 368-389

Why dead: Used to be called from pkg/registration/handler.go to grant the api-server's user CanActAs <userParty> per registration in the old custodial model. Both call sites were removed in commit 766f169. The new external-party flow uses CanExecuteAsAnyParty (wildcard) instead, so per-user grants are not needed.

Verification: grep -rn "GrantActAsParty" pkg/ scripts/ cmd/ returns only the interface declaration and implementation. Zero callers, even in tests.

Confidence: HIGH

Removal scope: ~25 lines (interface decl + implementation).

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2. Client.AllocateParty — wrapper is dead, raw protobuf is used directly

File: pkg/cantonsdk/identity/client.go — interface decl line 32, implementation lines 77-97

Why dead: Replaced by AllocateExternalParty and AllocateExternalPartyWithSignature in 766f169. The wrapper Client.AllocateParty still exists but has no callers via the identity client. The one place that does still allocate internal parties — scripts/testing/test-cip56-multi-participant.go:607, 650 — calls c.PartyAdmin().AllocateParty(...) directly against the raw protobuf service, not the wrapper.

Verification: No matches for Identity.AllocateParty or c.identity.AllocateParty in production code.

Confidence: HIGH

Removal scope: ~22 lines.

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3. Client.GetParticipantID — fully dead

File: pkg/cantonsdk/identity/client.go — interface decl line 35, implementation lines 251-259

Why dead: Added in 766f169 for completeness/parity but never wired into any production code path or test.

Verification: Zero callers anywhere in the repo.

Confidence: HIGH

Removal scope: ~10 lines.

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4. Client.ListParties — only used by an excluded utility script

File: pkg/cantonsdk/identity/client.go — interface decl line 34, implementation lines 223-249

Why dead-ish: Old fallback for the "party already exists" error path of AllocateParty; that path was deleted in 766f169 (AllocateExternalParty handles already-allocated cases via gRPC status codes).

Caveat: One caller still exists — scripts/utils/list-parties.go:138 calls cantonClient.Identity.ListParties(ctx). But that file is build-tagged //go:build ignore and is only run manually. Two options when cleaning up:

• (a) Delete both — remove ListParties from the identity client AND delete scripts/utils/list-parties.go if it's no longer maintained.
• (b) Keep both — leave ListParties and the utility script alone, since the script still has operational value for debugging.

I lean (a) since the script is //go:build ignore (not in CI, not built by default) and the same data is reachable via raw c.PartyAdmin().ListKnownParties(...) if needed in the future.

Confidence: MEDIUM (depends on whether we want to keep the utility)

Removal scope: ~30 lines from client.go + the constant listKnownPartiesPageSize (line 21) becomes dead with it. Plus optionally deleting scripts/utils/list-parties.go (~150 lines).

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5. KeyManagement.KeyDerivation config field — declared but never read

File: pkg/config/config.go:112-113

// KeyDerivation specifies how to generate Canton keys: "generate" (random) or "derive" (from EVM + seed)
KeyDerivation string `yaml:"key_derivation" default:"generate" validate:"required,oneof=generate derive"`

Why dead: Intent was to switch between random key generation and EVM-seed-derived keys. Only random generation was ever implemented (keys.GenerateCantonKeyPair is unconditional at pkg/user/service/service.go:162, 275). KeyDerivation is validated at config load but never read at runtime.

Verification: grep -rn KeyDerivation pkg/ scripts/ cmd/ returns only the field declaration in config.go and the default-value assertion in config_test.go:159. Nothing reads it in production.

Note: KeyManagement.MasterKeyEnv (the same struct's other field) IS alive — used at pkg/app/api/server.go:200, 204 to read the master encryption key. So we keep the struct, drop only the KeyDerivation field.

Confidence: HIGH (with the proviso that we should also remove the key_derivation: keys from default YAML configs)

Removal scope: 2 lines in config.go + ~5 entries across pkg/config/defaults/*.yaml files + 1 test assertion.

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What's NOT dead (deliberately verified)

To save reviewers re-checking these:

• pkg/keys/canton_keys.go is alive — keys.GenerateCantonKeyPair is called from custodial registration (pkg/user/service/service.go:162, 275) and several testing scripts.
• Custodial private-key encryption + storage is alive — the api-server still encrypts CantonPrivateKey and stores it as canton_private_key_encrypted for custodial / Canton-native registrations. See pkg/user/service/service.go:193, pkg/userstore/pg.go:140, pkg/userstore/model.go:21.
• RegisterCantonNativeUser is alive — supports Canton-native (Loop wallet) registration. pkg/user/service/service.go:218.
• KeyManagement.MasterKeyEnv is alive (same struct as the dead KeyDerivation).
• pkg/keys/store.go doesn't exist — already deleted.

Suggested approach

Single PR, mechanical removals:

1. Delete GrantActAsParty, AllocateParty, GetParticipantID from the identity client (interface + impl).
2. Remove KeyDerivation field from KeyManagement struct and from default YAML configs (config.api-server.{docker,local-devnet,mainnet}.yaml).
3. Decision call on ListParties:
   • If we drop the utility script: remove ListParties and listKnownPartiesPageSize from the identity client, delete scripts/utils/list-parties.go.
   • If we keep the utility script: leave both in place.
4. Run go build ./..., go test ./..., golangci-lint run to confirm nothing breaks.
5. Update pkg/cantonsdk/identity/mocks/ regenerate (make generate-mocks) if interface methods change.

Trigger

Came up while reviewing rights granted to the shared Canton OAuth user (#243). The unused GrantActAsParty was the obvious one; sweep found the others.