Add support of xAI and their Grok-2 model

Close #1630

pr_agent/algo/__init__.py

@@ -82,6 +82,9 @@ MAX_TOKENS = {
     'groq/llama-3.3-70b-versatile': 128000,
     'groq/mixtral-8x7b-32768': 32768,
     'groq/gemma2-9b-it': 8192,
+    'xai/grok-2': 131072,
+    'xai/grok-2-1212': 131072,
+    'xai/grok-2-latest': 131072,
     'ollama/llama3': 4096,
     'watsonx/meta-llama/llama-3-8b-instruct': 4096,
     "watsonx/meta-llama/llama-3-70b-instruct": 4096,

pr_agent/algo/ai_handlers/litellm_ai_handler.py

@@ -67,6 +67,8 @@ class LiteLLMAIHandler(BaseAiHandler):
             litellm.api_key = get_settings().groq.key
         if get_settings().get("REPLICATE.KEY", None):
             litellm.replicate_key = get_settings().replicate.key
+        if get_settings().get("XAI.KEY", None):
+            litellm.api_key = get_settings().xai.key
         if get_settings().get("HUGGINGFACE.KEY", None):
             litellm.huggingface_key = get_settings().huggingface.key
         if get_settings().get("HUGGINGFACE.API_BASE", None) and 'huggingface' in get_settings().config.model:

pr_agent/settings/.secrets_template.toml

@@ -32,6 +32,9 @@ key = "" # Optional, uncomment if you want to use Replicate. Acquire through htt
 [groq]
 key = "" # Acquire through https://console.groq.com/keys
 
+[xai]
+key = "" # Optional, uncomment if you want to use xAI. Acquire through https://console.x.ai/
+
 [huggingface]
 key = "" # Optional, uncomment if you want to use Huggingface Inference API. Acquire through https://huggingface.co/docs/api-inference/quicktour
 api_base = "" # the base url for your huggingface inference endpoint