fix(back):allow helpt text to be empte on signup form serializer NOCHANGELOG

api/funkwhale_api/common/schema.yml

@@ -20491,7 +20491,6 @@ components:
         text:
           type: string
           nullable: true
-          minLength: 1
           maxLength: 5000
         content_type:
           $ref: '#/components/schemas/ContentTypeEnum'

api/funkwhale_api/common/serializers.py

@@ -321,7 +321,9 @@ class AttachmentSerializer(serializers.Serializer):
 
 class ContentSerializer(serializers.Serializer):
     text = serializers.CharField(
-        max_length=models.CONTENT_TEXT_MAX_LENGTH, allow_null=True
+        max_length=models.CONTENT_TEXT_MAX_LENGTH,
+        allow_null=True,
+        allow_blank=True,
     )
     content_type = serializers.ChoiceField(
         choices=models.CONTENT_TEXT_SUPPORTED_TYPES,