add: app_data api

crates/core/src/model/mod.rs

@@ -51,6 +51,7 @@ pub enum Error {
     QuestionsDisabled,
     RequiresSupporter,
     DrawingsDisabled,
+    AppHitStorageLimit,
     Unknown,
 }
 
@@ -75,6 +76,7 @@ impl Display for Error {
             Self::QuestionsDisabled => "You are not allowed to ask questions there".to_string(),
             Self::RequiresSupporter => "Only site supporters can do this".to_string(),
             Self::DrawingsDisabled => "You are not allowed to submit drawings there".to_string(),
+            Self::AppHitStorageLimit => "This app has already hit its storage limit, or will do so if this data is processed.".to_string(),
             _ => format!("An unknown error as occurred: ({:?})", self),
         })
     }