Add datatype for is_spent sqlite column

Although, Sqlite column accepts
values of any type, it is
important to annotate this column
to make it easy to reason about.

src/database/sqlite.rs

@@ -52,6 +52,11 @@ static MIGRATIONS: &[&str] = &[
     "DELETE FROM transactions;",
     "DELETE FROM utxos;",
     "DROP INDEX idx_txid_vout;",
+    "CREATE UNIQUE INDEX idx_utxos_txid_vout ON utxos(txid, vout);",
+    "ALTER TABLE utxos RENAME TO utxos_old;",
+    "CREATE TABLE utxos (value INTEGER, keychain TEXT, vout INTEGER, txid BLOB, script BLOB, is_spent BOOLEAN DEFAULT 0);",
+    "INSERT INTO utxos SELECT value, keychain, vout, txid, script, is_spent FROM utxos_old;",
+    "DROP TABLE utxos_old;",
     "CREATE UNIQUE INDEX idx_utxos_txid_vout ON utxos(txid, vout);"
 ];