encrypt/decrypt and db interaction

src-tauri/migrations/20221201002355_initial.sql

@@ -1,9 +1,9 @@
 -- Add migration script here
 CREATE TABLE credentials (
-    access_key_id TEXT,
-    secret_key BLOB, -- encrypted
-    nonce BLOB,
-    expires INTEGER
+    access_key_id TEXT NOT NULL,
+    secret_key_enc BLOB NOT NULL,
+    salt BLOB NOT NULL,
+    nonce BLOB NOT NULL
 );
 
 CREATE TABLE config (