add initial implementation of auth gateway with models, routes, and session management

containers/auth-gateway/auth_gateway/models/session.py

@@ -0,0 +1,26 @@
+from datetime import datetime
+
+from pydantic import BaseModel, Field
+
+
+class SessionRecord(BaseModel):
+    session_id: str
+    created_at: datetime
+    updated_at: datetime
+    expires_at: datetime
+    username: str | None = None
+    email: str | None = None
+    subject: str | None = None
+    groups: list[str] = Field(default_factory=list)
+    auth_factors: list[str] = Field(default_factory=list)
+    metadata: dict = Field(default_factory=dict)
+
+
+class OIDCStateRecord(BaseModel):
+    state: str
+    nonce: str
+    method_name: str
+    host: str
+    next_url: str
+    created_at: datetime
+    expires_at: datetime