feat(sdk)!: pure DPNS and DashPay document builders shared with embedders

[PastaPastaPasta]

Issue being fixed or feature implemented

Stacked on #4631 (review from feat(sdk) onward). Carries forward the pure-builder half of #4619, without that PR's request-driven FromProof<GetDocumentsRequest> verifier, which the SDK-first C++ embedding (dashpay/dash#7512, next PR in this series) no longer needs: the SDK retains the rich query it built and verifies against it, so no wire request is reconstructed from bytes.

dash-sdk's register_dpns_name and create_contact_request assemble DPNS and DashPay documents inline. An embedder that signs with a wallet-held key (Dash Core's platform GUI) needs the same assembly as a pure function over caller-supplied entropy, salt and ciphertexts, and must not reimplement it in C++.

What was done?

Pure document builders, in dash-platform-queries:

• dpns_usernames::{build_dpns_preorder_document, build_dpns_domain_document, salted_domain_hash} and dashpay::build_contact_request_document, the assembly halves of dash-sdk's register_dpns_name / create_contact_request as pure functions. dash-sdk's networked flows now call them.
• They reuse what exists: normalization is dpp's consensus convert_to_homograph_safe_chars (the crate's to_ascii_lowercase copy, which differed from the data trigger on non-ASCII input, is replaced by a re-export); the preorder commitment uses dpp::util::hash::hash_double; property names come from the dpns-contract / dashpay-contract constants; the DashPay byte bounds are read from the contract schema's DocumentPropertyType sizes. The domain builder rejects a label the contract pattern refuses before a preorder is paid for.
• The entropy/document-id consistency check moves into dpp's DocumentCreateTransitionV0::from_document, so every create-transition caller (SDK, wasm, FFI, embedders) inherits it instead of remembering an opt-in helper; it fails with the same InvalidDocumentTransitionIdError Drive would return after the nonce bump. dash-sdk's private ensure_entropy_matches_document_id is removed.

How Has This Been Tested?

• dash-platform-queries: 61 lib tests pass, including builder tests against the real DPNS/DashPay system contracts (preorder commitment matches the domain document's salt+label, id derivation, label-pattern rejection, schema byte-bound enforcement).
• dpp: from_document_refuses_an_id_the_entropy_does_not_derive; the document_create_transition suites pass.
• dash-sdk --lib: 185 pass. cargo fmt --check clean.
• Not done here: a live-network run of register_dpns_name / send_contact_request; the on-wire behaviour is byte-identical by construction (assembly moved, not changed) and the unit tests pin the property maps. The C++ crate in the next PR pins the transitions built from these documents byte for byte against rs-dpp-generated vectors.

Breaking Changes

API shape on unreleased v4.2-dev (not on crates.io): dash_sdk::platform::dashpay::ContactRequestResult now carries the assembled document plus entropy instead of id / owner_id / properties. No consumer outside rs-sdk uses it. register_dpns_name now rejects a label the DPNS contract pattern refuses locally instead of after the preorder is broadcast.

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have added "!" to the title and described breaking changes in the corresponding section if my code contains any
• I have made corresponding changes to the documentation if needed

For repository code-owners and collaborators only

• I have assigned this pull request to a milestone

[coderabbitai]

Important

Draft PR not reviewed

Draft PRs are not automatically reviewed by default.

• Trigger a manual review

To automatically review draft PRs, update your CodeRabbit configuration:

reviews:
  auto_review:
    drafts: true

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}