feat(crypto): Add a store error variant for breaking database format changes

crates/matrix-sdk-crypto/src/store/mod.rs

@@ -597,6 +597,14 @@ pub enum CryptoStoreError {
     /// The store failed to (de)serialize a data type.
     #[error(transparent)]
     Serialization(#[from] SerdeError),
+
+    /// The database format has changed in a backwards incompatible way.
+    #[error(
+        "The database format changed in an incompatible way, current \
+        version: {0}, latest version: {1}"
+    )]
+    UnsupportedDatabaseVersion(usize, usize),
+
     /// A problem with the underlying database backend
     #[error(transparent)]
     Backend(#[from] anyhow::Error),

crates/matrix-sdk-sled/src/cryptostore.rs

@@ -486,11 +486,10 @@ impl SledStore {
         }
 
         if version <= 3 {
-            return Err(anyhow!(
-                "Unsupported database version, the database \
-                 format changed in a backwards incompatible way"
-            )
-            .into());
+            return Err(CryptoStoreError::UnsupportedDatabaseVersion(
+                version.into(),
+                DATABASE_VERSION.into(),
+            ));
         }
 
         self.inner