Add Flyway, run db migration in local PostgreSQL db

First step in my plan to switch away from MySQL.

src/main/java/database/migration/FlywayRunner.java

@@ -0,0 +1,22 @@
+package database.migration;
+
+import database.PgDatabaseConfig;
+import org.flywaydb.core.Flyway;
+import org.flywaydb.core.api.FlywayException;
+
+public class FlywayRunner {
+    private final PgDatabaseConfig dbConfig;
+
+    public FlywayRunner(PgDatabaseConfig dbConfig) {
+        this.dbConfig = dbConfig;
+    }
+
+    public void migrate() throws FlywayException {
+        Flyway flyway = Flyway.configure()
+                .dataSource(dbConfig.getJdbcUrl(), dbConfig.adminUsername(), dbConfig.adminPassword())
+                .schemas(dbConfig.schema())
+                .createSchemas(true)
+                .load();
+        flyway.migrate();
+    }
+}