fix: add http error responses (#494)

This features adds rfc7807 Problem detail responses when an error happens processing a request.

This will greatly improve the common issues  with "blank pages" and "404 pages" issues which should now properly tell the user what input was wrong (group that does not exist, container name that does not exist, etc.)

internal/api/start_blocking.go

@@ -0,0 +1,59 @@
+package api
+
+import (
+	"errors"
+	"github.com/gin-gonic/gin"
+	"github.com/sablierapp/sablier/app/http/routes"
+	"github.com/sablierapp/sablier/app/http/routes/models"
+	"github.com/sablierapp/sablier/app/sessions"
+	"net/http"
+)
+
+func StartBlocking(router *gin.RouterGroup, s *routes.ServeStrategy) {
+	router.GET("/strategies/blocking", func(c *gin.Context) {
+		request := models.BlockingRequest{
+			Timeout: s.StrategyConfig.Blocking.DefaultTimeout,
+		}
+
+		if err := c.ShouldBind(&request); err != nil {
+			AbortWithProblemDetail(c, ProblemValidation(err))
+			return
+		}
+
+		if len(request.Names) == 0 && request.Group == "" {
+			AbortWithProblemDetail(c, ProblemValidation(errors.New("'names' or 'group' query parameter must be set")))
+			return
+		}
+
+		if len(request.Names) > 0 && request.Group != "" {
+			AbortWithProblemDetail(c, ProblemValidation(errors.New("'names' and 'group' query parameters are both set, only one must be set")))
+			return
+		}
+
+		var sessionState *sessions.SessionState
+		var err error
+		if len(request.Names) > 0 {
+			sessionState, err = s.SessionsManager.RequestReadySession(c.Request.Context(), request.Names, request.SessionDuration, request.Timeout)
+		} else {
+			sessionState, err = s.SessionsManager.RequestReadySessionGroup(c.Request.Context(), request.Group, request.SessionDuration, request.Timeout)
+			var groupNotFoundError sessions.ErrGroupNotFound
+			if errors.As(err, &groupNotFoundError) {
+				AbortWithProblemDetail(c, ProblemGroupNotFound(groupNotFoundError))
+				return
+			}
+		}
+		if err != nil {
+			AbortWithProblemDetail(c, ProblemError(err))
+			return
+		}
+
+		if sessionState == nil {
+			AbortWithProblemDetail(c, ProblemError(errors.New("session could not be created, please check logs for more details")))
+			return
+		}
+
+		AddSablierHeader(c, sessionState)
+
+		c.JSON(http.StatusOK, map[string]interface{}{"session": sessionState})
+	})
+}