✨ feat: refactor environment variable initialization and introduce new constant types for API and context keys

constant/endpoint_type.go

@@ -0,0 +1,11 @@
+package constant
+
+type EndpointType string
+
+const (
+	EndpointTypeOpenAI         EndpointType = "openai"
+	EndpointTypeOpenAIResponse EndpointType = "openai-response"
+	EndpointTypeAnthropic      EndpointType = "anthropic"
+	EndpointTypeGemini         EndpointType = "gemini"
+	EndpointTypeJinaRerank     EndpointType = "jina-rerank"
+)