feat(motoko): add Motoko client generator

[ggreif]

Summary

This PR adds a Motoko client generator for OpenAPI Generator, targeting the Internet Computer (IC) platform.

Motoko is the native smart-contract language for the IC. The generated client makes HTTP outcalls from IC canisters using the Management Canister's http_request API, and uses the serde Mops package for JSON serialization/deserialization.

Files included

Generator implementation

• modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/MotokoClientCodegen.java

Mustache templates (6 files)

• modules/openapi-generator/src/main/resources/motoko/api.mustache
• modules/openapi-generator/src/main/resources/motoko/model.mustache
• modules/openapi-generator/src/main/resources/motoko/enum.mustache
• modules/openapi-generator/src/main/resources/motoko/Config.mustache
• modules/openapi-generator/src/main/resources/motoko/README.mustache
• modules/openapi-generator/src/main/resources/motoko/mops.toml.mustache

Tests

• modules/openapi-generator/src/test/java/org/openapitools/codegen/motoko/MotokoClientCodegenTest.java
• modules/openapi-generator/src/test/java/org/openapitools/codegen/motoko/MotokoClientCodegenModelTest.java
• modules/openapi-generator/src/test/java/org/openapitools/codegen/motoko/MotokoClientCodegenOptionsTest.java
• modules/openapi-generator/src/test/java/org/openapitools/codegen/options/MotokoClientCodegenOptionsProvider.java

Registration & sample configs

• modules/openapi-generator/src/main/resources/META-INF/services/org.openapitools.codegen.CodegenConfig — single-line addition registering MotokoClientCodegen
• docs/generators.md — single-line addition listing motoko (beta) in the client generators section
• bin/configs/motoko-petstore-new.yaml — petstore sample config (with dfx)
• bin/configs/motoko-petstore-nodfx.yaml — petstore sample config (without dfx)

Validation

Generation was tested against the standard petstore spec (modules/openapi-generator/src/test/resources/3_0/petstore.yaml). The generator produced:

• src/Apis/PetApi.mo, StoreApi.mo, UserApi.mo — API client modules
• src/Models/Pet.mo, Order.mo, User.mo, etc. — model types with JSON serialization
• src/Config.mo — canister configuration
• mops.toml, README.md — project metadata

The generated .mo files include correct IC Management Canister HTTP outcall types, proper Motoko module structure, and serde-based JSON encoding/decoding.

Generator features

• Generates IC canister-compatible HTTP client code in Motoko
• Supports both replicated and non-replicated query calls
• Configurable: useDfx option to generate dfx deployment configuration
• Handles enums, optional fields, arrays, and nested models
• Uses mops package manager conventions

🤖 Generated with Claude Code

---

Summary by cubic

Adds a new motoko client generator for Internet Computer canisters using Management Canister http_request and serde JSON. Includes a committed Petstore sample and icp.yaml scaffolding via a new useIcp option alongside useDfx.

• New Features

  • MotokoClientCodegen with templates: api, model, enum, Config, README, mops.toml, icp.yaml.
  • IC HTTP outcalls (replicated/non‑replicated), transform hook, shared Config; auth: bearer, API key, basic.
  • Options: useDfx and useIcp; both enable useImportedInterface to import ic:aaaaa-aa (inline types when neither).
  • serde JSON for enums/oneOf, arrays, maps, optionals; auto‑convert non‑negative Int to Nat.
  • Registered generator and docs at docs/generators/motoko.md; Petstore sample at samples/client/petstore/motoko; sample config at bin/configs/motoko-petstore.yaml; unit tests added.

• Bug Fixes

  • Enforce mutual exclusivity for useDfx and useIcp (throws if both); CLI help and docs updated.
  • Cleaned up bin/configs/motoko-petstore.yaml to remove -nodfx suffixes in outputDir and artifactId.

^{Written for commit cfc8e66. Summary will update on new commits.}