Feat: add model provider DeepInfra (#9003)

### What problem does this PR solve?

Add model provider DeepInfra. This model list comes from our community. 

NOTE: most endpoints haven't been tested, but they should work as OpenAI
does.

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

rag/llm/embedding_model.py

@@ -202,9 +202,10 @@ class QWenEmbed(Base):
         self.model_name = model_name
 
     def encode(self, texts: list):
-        import dashscope
         import time
 
+        import dashscope
+
         batch_size = 4
         res = []
         token_count = 0
@@ -900,3 +901,12 @@ class GiteeEmbed(SILICONFLOWEmbed):
         if not base_url:
             base_url = "https://ai.gitee.com/v1/embeddings"
         super().__init__(key, model_name, base_url)
+
+
+class DeepInfraEmbed(OpenAIEmbed):
+    _FACTORY_NAME = "DeepInfra"
+
+    def __init__(self, key, model_name, base_url="https://api.deepinfra.com/v1/openai"):
+        if not base_url:
+            base_url = "https://api.deepinfra.com/v1/openai"
+        super().__init__(key, model_name, base_url)