Unique username

loon/web/users/models.py

@@ -4,6 +4,6 @@ from sqlmodel import SQLModel, Field
 class User(SQLModel, table=True):
     id: int = Field(default=None, primary_key=True)
     uuid: str = Field(unique=True)
-    internal_username: str
+    internal_username: str = Field(unique=True)
     password: str
     admin: bool = Field(default=False)