feat: implement channel runtime connectors

app-instance/backend/beaver/foundation/config/schema.py

@@ -91,6 +91,19 @@ class AuthzConfig:
     outlook_mcp_url: str = ""
 
 
+@dataclass(slots=True)
+class ChannelConfig:
+    """One configured channel adapter instance."""
+
+    enabled: bool = False
+    kind: str = ""
+    mode: str = "webhook"
+    account_id: str = ""
+    display_name: str = ""
+    config: dict[str, Any] = field(default_factory=dict)
+    secrets: dict[str, str] = field(default_factory=dict)
+
+
 @dataclass(slots=True)
 class BackendIdentityConfig:
     """This backend's AuthZ client identity."""
@@ -111,6 +124,7 @@ class BeaverConfig:
     embedding: EmbeddingConfig = field(default_factory=EmbeddingConfig)
     tools: ToolsConfig = field(default_factory=ToolsConfig)
     authz: AuthzConfig = field(default_factory=AuthzConfig)
+    channels: dict[str, ChannelConfig] = field(default_factory=dict)
     backend_identity: BackendIdentityConfig = field(default_factory=BackendIdentityConfig)
     config_path: Path | None = None