Validate tags with regex

domain/src/main/kotlin/validation/NoteValidations.kt

@@ -22,6 +22,9 @@ internal object NoteValidations {
         NoteMetadata::tags onEach {
             maxLength(15)
             addConstraint("must not be blank") { it.isNotBlank() }
+            addConstraint("must only contain alphanumeric characters, `-` and `_`") {
+                it.matches("^[a-zA-Z0-9-_]+\$".toRegex())
+            }
         }
     }