Dav Push: Logic to register subscriptions

crates/store/src/subscription_store.rs

@@ -0,0 +1,19 @@
+use crate::Error;
+use async_trait::async_trait;
+use chrono::NaiveDateTime;
+
+pub struct Subscription {
+    pub id: String,
+    pub topic: String,
+    pub expiration: NaiveDateTime,
+    pub push_resource: String,
+}
+
+#[async_trait(?Send)]
+pub trait SubscriptionStore: Send + Sync + 'static {
+    async fn get_subscriptions(&self, topic: &str) -> Result<Vec<Subscription>, Error>;
+    async fn get_subscription(&self, id: &str) -> Result<Subscription, Error>;
+    /// Returns whether a subscription under the id already existed
+    async fn upsert_subscription(&self, sub: Subscription) -> Result<bool, Error>;
+    async fn delete_subscription(&self, id: &str) -> Result<(), Error>;
+}