feat: add developer message (#192)

Author: Nov1c444

python/dify_plugin/entities/model/message.py

@@ -14,6 +14,7 @@ class PromptMessageRole(Enum):
     USER = "user"
     ASSISTANT = "assistant"
     TOOL = "tool"
+    DEVELOPER = "developer"
 
     @classmethod
     def value_of(cls, value: str) -> "PromptMessageRole":
@@ -242,6 +243,14 @@ class SystemPromptMessage(PromptMessage):
     role: PromptMessageRole = PromptMessageRole.SYSTEM
 
 
+class DeveloperPromptMessage(PromptMessage):
+    """
+    Model class for developer prompt message.
+    """
+
+    role: PromptMessageRole = PromptMessageRole.DEVELOPER
+
+
 class ToolPromptMessage(PromptMessage):
     """
     Model class for tool prompt message.