feat: user defined custom tools as part of workflow execution (#94)

* feat: add custom tools functionality

* Show tools in nodes

* integrate tool calling with pipeline engine

api/utils/credential_auth.py

@@ -0,0 +1,95 @@
+"""Build HTTP authentication headers from ExternalCredentialModel.
+
+This module provides functions for constructing HTTP authentication headers
+from ExternalCredentialModel instances. Used by both webhook integrations
+and custom tool execution.
+"""
+
+import base64
+from typing import TYPE_CHECKING, Any, Dict, Optional
+
+if TYPE_CHECKING:
+    from api.db.models import ExternalCredentialModel
+
+
+def build_auth_header(credential: "ExternalCredentialModel") -> Dict[str, str]:
+    """Build authentication header based on credential type.
+
+    Supports the following credential types:
+    - bearer_token: Authorization: Bearer <token>
+    - api_key: Custom header with API key
+    - basic_auth: Authorization: Basic <base64(username:password)>
+    - custom_header: Any custom header name/value pair
+
+    Args:
+        credential: The ExternalCredentialModel instance
+
+    Returns:
+        Dict with header name and value, or empty dict if credential type
+        is not recognized or is 'none'
+    """
+    cred_type = credential.credential_type
+    cred_data = credential.credential_data or {}
+
+    if cred_type == "bearer_token":
+        token = cred_data.get("token", "")
+        return {"Authorization": f"Bearer {token}"}
+
+    elif cred_type == "api_key":
+        header_name = cred_data.get("header_name", "X-API-Key")
+        api_key = cred_data.get("api_key", "")
+        return {header_name: api_key}
+
+    elif cred_type == "basic_auth":
+        username = cred_data.get("username", "")
+        password = cred_data.get("password", "")
+        encoded = base64.b64encode(f"{username}:{password}".encode()).decode()
+        return {"Authorization": f"Basic {encoded}"}
+
+    elif cred_type == "custom_header":
+        header_name = cred_data.get("header_name", "X-Custom")
+        header_value = cred_data.get("header_value", "")
+        return {header_name: header_value}
+
+    return {}
+
+
+def build_auth_header_from_data(
+    credential_type: str,
+    credential_data: Optional[Dict[str, Any]] = None,
+) -> Dict[str, str]:
+    """Build authentication header from raw credential data.
+
+    This is a convenience function when you have credential data
+    directly rather than a full ExternalCredentialModel.
+
+    Args:
+        credential_type: Type of credential (bearer_token, api_key, etc.)
+        credential_data: Dict containing credential-specific fields
+
+    Returns:
+        Dict with header name and value
+    """
+    cred_data = credential_data or {}
+
+    if credential_type == "bearer_token":
+        token = cred_data.get("token", "")
+        return {"Authorization": f"Bearer {token}"}
+
+    elif credential_type == "api_key":
+        header_name = cred_data.get("header_name", "X-API-Key")
+        api_key = cred_data.get("api_key", "")
+        return {header_name: api_key}
+
+    elif credential_type == "basic_auth":
+        username = cred_data.get("username", "")
+        password = cred_data.get("password", "")
+        encoded = base64.b64encode(f"{username}:{password}".encode()).decode()
+        return {"Authorization": f"Basic {encoded}"}
+
+    elif credential_type == "custom_header":
+        header_name = cred_data.get("header_name", "X-Custom")
+        header_value = cred_data.get("header_value", "")
+        return {header_name: header_value}
+
+    return {}