add basic user authentication

internal/api/dto.go

@@ -6,7 +6,12 @@ type bookPostCreate struct {
 	Rating int    `json:"rating" binding:"min=0,max=10"`
 }
 
-type userPostCreate struct {
+type userSignup struct {
+	Username string `json:"username" binding:"required,min=2,max=20"`
+	Password string `json:"password" binding:"required,min=6,max=100"`
+}
+
+type userLogin struct {
 	Username string `json:"username" binding:"required,min=2,max=20"`
 	Password string `json:"password" binding:"required,min=6,max=100"`
 }