fix(model_providers/vertex_ai): Vertex AI Anthropic models authentication failed (#4971)

api/core/model_runtime/model_providers/vertex_ai/llm/llm.py

 from typing import Optional, Union, cast
 
 import google.api_core.exceptions as exceptions
+import google.auth.transport.requests
 import vertexai.generative_models as glm
 from anthropic import AnthropicVertex, Stream
 from anthropic.types import (
 
 logger = logging.getLogger(__name__)
 
-GEMINI_BLOCK_MODE_PROMPT = """You should always follow the instructions and output a valid {{block}} object.
-The structure of the {{block}} object you can found in the instructions, use {"answer": "$your_answer"} as the default structure
-if you are not sure about the structure.
-
-<instructions>
-{{instructions}}
-</instructions>
-"""
-
 
 class VertexAiLargeLanguageModel(LargeLanguageModel):
 
         """
         # use Anthropic official SDK references
         # - https://github.com/anthropics/anthropic-sdk-python
+        service_account_info = json.loads(base64.b64decode(credentials["vertex_service_account_key"]))
         project_id = credentials["vertex_project_id"]
+        SCOPES = ["https://www.googleapis.com/auth/cloud-platform"]
+        token = ''
 
+        # get access token from service account credential
+        if service_account_info:
+            credentials = service_account.Credentials.from_service_account_info(service_account_info, scopes=SCOPES)
+            request = google.auth.transport.requests.Request()
+            credentials.refresh(request)
+            token = credentials.token
+
+        # Vertex AI Anthropic Claude3 Opus model avaiable in us-east5 region, Sonnet and Haiku avaiable in us-central1 region
         if 'opus' in model:
             location = 'us-east5'
         else:
             location = 'us-central1'
-            
-        client = AnthropicVertex(
-            region=location, 
-            project_id=project_id
-        )
+        
+        # use access token to authenticate
+        if token:
+            client = AnthropicVertex(
+                region=location, 
+                project_id=project_id,
+                access_token=token
+            )
+        # When access token is empty, try to use the Google Cloud VM's built-in service account or the GOOGLE_APPLICATION_CREDENTIALS environment variable
+        else:
+            client = AnthropicVertex(
+                region=location, 
+                project_id=project_id,
+            )
 
         extra_model_kwargs = {}
         if stop:
             aiplatform.init(project=project_id, location=location)
 
         history = []
-        system_instruction = GEMINI_BLOCK_MODE_PROMPT
+        system_instruction = ""
         # hack for gemini-pro-vision, which currently does not support multi-turn chat
         if model == "gemini-1.0-pro-vision-001":
             last_msg = prompt_messages[-1]