add LGAR model; WIP

python/ngen_conf/src/ngen/config/lgar.py

@@ -0,0 +1,16 @@
+from typing import Literal, Optional, Mapping
+from pydantic import Field
+
+from .bmi_formulation import BMICxx
+
+
+class LGAR(BMICxx):
+    """A BMICXX implementation for the LGAR ngen module"""
+
+    model_params: Optional[Mapping[str, str]]
+    # FIXME this isn't required for CXX bmi in ngen?
+    registration_function: str = "none"
+    # NOTE aliases don't propagate to subclasses, so we have to repeat the alias
+    model_name: Literal["LGAR"] = Field(
+        "LGAR", const=True, alias="model_type_name"
+    )