GeezerVison

Problem

Generated service methods pass typed request DTOs (pydantic BaseModel) straight to httpx json=. httpx uses plain json.dumps (no default=), which cannot serialize BaseModel — every typed POST/PUT method (create_contact, update_contact, upsert_contact, create_note, add_tags, ...) crashes with TypeError before reaching the network. Only plain-dict bodies work.

Fix

• New serialize_payload() in src/highlevel/utils/request_utils.py: model_dump(exclude_none=True) for BaseModel, recursive for dict/list, passthrough for primitives, None stays None.
• Wrapped all 291 call sites across 42 service files; import updated identically everywhere.

Verification

• py_compile clean on all 43 modified files
• serialize_payload(CreateContactDtoV3(locationId, firstName, email, customFields=[{key: event_id, fieldValue: ...}])) → JSON-serializable dict with exact customFields shape preserved
• Edge cases pass: None → None, dict → passthrough, list of models → list of dicts
• No behavior change for existing dict-based callers (passthrough)

Impact

Unblocks every typed-body method in the SDK (the most common usage per the README). ~10 lines of real logic in one place.