adding static connection

app/models/static_connection.py

@@ -0,0 +1,13 @@
+from sqlalchemy import Float, UniqueConstraint
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.core.database import Base
+
+
+class StaticConnection(Base):
+    __tablename__ = "static_connections"
+    __table_args__ = (UniqueConstraint("od_mm"),)
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    od_mm: Mapped[float] = mapped_column(Float, nullable=False)
+    od_in: Mapped[float] = mapped_column(Float, nullable=False)