feat(api/workflow): Add Conversation.dialogue_count (#7275)

api/core/workflow/enums.py

@@ -0,0 +1,25 @@
+from enum import Enum
+
+
+class SystemVariable(str, Enum):
+    """
+    System Variables.
+    """
+    QUERY = 'query'
+    FILES = 'files'
+    CONVERSATION_ID = 'conversation_id'
+    USER_ID = 'user_id'
+    DIALOGUE_COUNT = 'dialogue_count'
+
+    @classmethod
+    def value_of(cls, value: str):
+        """
+        Get value of given system variable.
+
+        :param value: system variable value
+        :return: system variable
+        """
+        for system_variable in cls:
+            if system_variable.value == value:
+                return system_variable
+        raise ValueError(f'invalid system variable value {value}')