sdk/middleware/sqgin: use the actual request context instead of gin's

Gin's context wrongly implements `context.Context` and doesn't wrap the
underlying request context at all. Therefore, we need to use the actual request
context `c.Request.Context()` so that the agent can properly manage the request
context, but also to correctly propagate values stored in the context.

sdk/middleware/sqgin/gin.go

@@ -76,7 +76,7 @@ func middlewareHandler(agent protection_context.AgentFace, c *gingonic.Context)
 	requestReader := &requestReaderImpl{c: c}
 	responseWriter := &responseWriterImpl{c: c}
 
-	ctx, reqCtx, cancelHandlerContext := http_protection.NewRequestContext(c, agent, responseWriter, requestReader)
+	ctx, reqCtx, cancelHandlerContext := http_protection.NewRequestContext(c.Request.Context(), agent, responseWriter, requestReader)
 	if ctx == nil {
 		c.Next()
 		return