🐛 fix(chains.py): set required=True for TemplateField 'memory'

✨ feat(chains.py): add TemplateField 'chain_type' to support different types of QA chains
The 'memory' field was previously set to required=False, but it is actually required for the chain to function properly. This fix sets required=True for the 'memory' field.

A new TemplateField 'chain_type' has been added to support different types of QA chains. This field is of type 'str', is required, and is a list of options. It allows the user to select the type of QA chain they want to use.

src/backend/langflow/template/frontend_node/chains.py

@@ -13,7 +13,7 @@ class ChainFrontendNode(FrontendNode):
             self.template.add_field(
                 TemplateField(
                     field_type="BaseChatMemory",
-                    required=False,
+                    required=True,
                     show=True,
                     name="memory",
                     advanced=False,
@@ -31,6 +31,19 @@ class ChainFrontendNode(FrontendNode):
                     display_name="Return source documents",
                 )
             )
+            self.template.add_field(
+                TemplateField(
+                    field_type="str",
+                    required=True,
+                    is_list=True,
+                    show=True,
+                    multiline=False,
+                    options=QA_CHAIN_TYPES,
+                    value=QA_CHAIN_TYPES[0],
+                    name="chain_type",
+                    advanced=False,
+                )
+            )
 
     @staticmethod
     def format_field(field: TemplateField, name: Optional[str] = None) -> None: