fix(CoUnitPromptGenerator): ensure retrofit service creation is consi…

…stent #51

To improve code readability and maintainability, the creation of the `CoUnitApi` service instance has been moved outside the `findIntention` and `semanticQuery` methods. Now, the service instance is initialized once and reused throughout the class, which aligns with the principles of software design by reducing code duplication and promoting the single responsibility principle.

src/main/kotlin/cc/unitmesh/devti/counit/CoUnitPromptGenerator.kt

@@ -18,14 +18,14 @@ class CoUnitPromptGenerator(val project: Project) {
         .addConverterFactory(GsonConverterFactory.create())
         .build()
 
-    var service: CoUnitApi = retrofit.create(CoUnitApi::class.java)
-
     fun findIntention(input: String): String? {
+        val service: CoUnitApi = retrofit.create(CoUnitApi::class.java)
         val body = service.explainQuery(input).execute().body()
         return body?.prompt
     }
 
     fun semanticQuery(query: ExplainQuery): QueryResult {
+        val service: CoUnitApi = retrofit.create(CoUnitApi::class.java)
         val englishQuery: QueryResponse? = service.query(query.query, PayloadType.OpenApi).execute().body()
         val hydeDoc: QueryResponse? = service.query(query.hypotheticalDocument, PayloadType.OpenApi).execute().body()
         val naturalLangQuery: QueryResponse? = service.query(query.natureLangQuery, PayloadType.OpenApi).execute().body()