Better contract. Explicit parameter usage

matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/crypto/keysbackup/KeysBackupVersionTrust.kt

@@ -24,7 +24,7 @@ data class KeysBackupVersionTrust(
          * Flag to indicate if the backup is trusted.
          * true if there is a signature that is valid & from a trusted device.
          */
-        val usable: Boolean = false,
+        val usable: Boolean,
 
         /**
          * Signatures found in the backup version.

matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/crypto/keysbackup/DefaultKeysBackupService.kt

@@ -413,13 +413,13 @@ internal class DefaultKeysBackupService @Inject constructor(
 
         if (authData == null || authData.publicKey.isEmpty() || authData.signatures.isNullOrEmpty()) {
             Timber.v("getKeysBackupTrust: Key backup is absent or missing required data")
-            return KeysBackupVersionTrust()
+            return KeysBackupVersionTrust(usable = false)
         }
 
         val mySigs = authData.signatures[userId]
         if (mySigs.isNullOrEmpty()) {
             Timber.v("getKeysBackupTrust: Ignoring key backup because it lacks any signatures from this user")
-            return KeysBackupVersionTrust()
+            return KeysBackupVersionTrust(usable = false)
         }
 
         var keysBackupVersionTrustIsUsable = false