2.0.0

Breaking changes

• The typed register helpers (read_uint16, read_int16, read_uint32,
  read_float32, read_string, write_uint16, write_float32) have been
  removed from the ModbusUnit protocol and every backend. The connection
  layer now exposes raw register/coil I/O plus the full Modbus function-code set
  only; datatype encoding/decoding moves one layer up (see below). Replace
  await unit.read_uint32(addr) with
  decode_uint32(await unit.read_holding_registers(addr, 2)).

New

• modbus_connection.decode / modbus_connection.encode — a pure,
  backend-neutral register codec covering the SunSpec point-type set: int/uint
  16·32·64, float32/64, strings, IPv4/IPv6/EUI-48, and weighted sums, in either
  word order.
• modbus_connection.model — an optional device-modelling framework. Map a
  device's registers and coils to typed Python attributes and read a whole device
  (or one sub-system) in as few Modbus calls as possible:
  • Component / ComponentGroup with pooled, range-aware, cached block-read
    planning.
  • Generic field factories: gauge, integer, uint32/64, int32/64,
    float32/64, string, raw_register, scaled_sum, enum / flags
    (native IntEnum / IntFlag mapping, incl. signed codes), and coil.
  • modbus_connection.model.sunspec — SunSpec point types pre-wired with their
    per-point "unimplemented" sentinels, plus address types and dynamic scale
    factors (sunssf).
  • Holding (FC03) and input (FC04) register spaces, planned and read separately.

The backends, the in-memory mock, and the pytest plugin are otherwise unchanged.