refactor: updated swagger;

feat: helper function in errors for checking postgres error types;
feat: sql query method for finding users by their email;
feat: registration begin/complete with checking existing username/email;
refactor: error handling in controller

backend/internal/controllers/auth.go

@@ -18,11 +18,13 @@
 package controllers
 
 import (
+	errs "easywish/internal/errors"
 	"easywish/internal/middleware"
 	"easywish/internal/models"
 	"easywish/internal/services"
 	"easywish/internal/utils"
 	"easywish/internal/utils/enums"
+	"errors"
 	"net/http"
 
 	"github.com/gin-gonic/gin"
@@ -96,6 +98,8 @@ func (a *authControllerImpl) Refresh(c *gin.Context) {
 // @Accept json
 // @Produce json
 // @Param request body models.RegistrationBeginRequest true "desc"
+// @Success 200 "Account is created and awaiting verification"
+// @Success 409 "Username or email is already taken"
 // @Router /auth/registrationBegin [post]
 func (a *authControllerImpl) RegistrationBegin(c *gin.Context) {
 
@@ -108,11 +112,15 @@ func (a *authControllerImpl) RegistrationBegin(c *gin.Context) {
 	_, err := a.authService.RegistrationBegin(request.Body)
 
 	if err != nil {
-		c.JSON(http.StatusBadRequest, err.Error())
+		if errors.Is(err, errs.ErrUsernameTaken) || errors.Is(err, errs.ErrEmailTaken) {
+			c.Status(http.StatusConflict)
+		} else {
+			c.Status(http.StatusInternalServerError)
+		}
 		return
 	}
 
-	c.Status(http.StatusAccepted)
+	c.Status(http.StatusOK)
 	return
 }
 
@@ -121,16 +129,37 @@ func (a *authControllerImpl) RegistrationBegin(c *gin.Context) {
 // @Tags Auth
 // @Accept json
 // @Produce json
+// @Param request body models.RegistrationCompleteRequest true "desc"
+// @Success 200 {object} models.RegistrationCompleteResponse "desc"
 // @Router /auth/registrationComplete [post]
 func (a *authControllerImpl) RegistrationComplete(c *gin.Context) {
-	c.Status(http.StatusNotImplemented)
+	request, ok := utils.GetRequest[models.RegistrationCompleteRequest](c)
+		if !ok {
+		c.Status(http.StatusBadRequest)
+		return
+	}
+
+	response, err := a.authService.RegistrationComplete(request.Body)
+
+	if err != nil {
+		if errors.Is(err, errs.ErrForbidden) {
+			c.Status(http.StatusForbidden)
+		} else if errors.Is(err, errs.ErrUnauthorized) {
+			c.Status(http.StatusUnauthorized)
+		} else {
+			c.Status(http.StatusInternalServerError)
+		}
+		return
+	}
+
+	c.JSON(http.StatusOK, response)
 }
 
 func (a *authControllerImpl) RegisterRoutes(group *gin.RouterGroup) {
     group.POST("/registrationBegin", middleware.RequestMiddleware[models.RegistrationBeginRequest](enums.GuestRole), a.RegistrationBegin)
-    group.POST("/registrationComplete", a.RegistrationComplete)
-    group.POST("/login", a.Login)
-    group.POST("/refresh", a.Refresh)
-    group.POST("/passwordResetBegin", a.PasswordResetBegin)
-    group.POST("/passwordResetComplete", a.PasswordResetComplete)
+    group.POST("/registrationComplete", middleware.RequestMiddleware[models.RegistrationCompleteRequest](enums.GuestRole), a.RegistrationComplete)
+    group.POST("/login", middleware.RequestMiddleware[models.RegistrationBeginRequest](enums.GuestRole), a.Login)
+    group.POST("/refresh", middleware.RequestMiddleware[models.RegistrationBeginRequest](enums.UserRole), a.Refresh)
+    group.POST("/passwordResetBegin", middleware.RequestMiddleware[models.RegistrationBeginRequest](enums.GuestRole), a.PasswordResetBegin)
+    group.POST("/passwordResetComplete", middleware.RequestMiddleware[models.RegistrationBeginRequest](enums.GuestRole), a.PasswordResetComplete)
 }