Add Flyway, run db migration in local PostgreSQL db

First step in my plan to switch away from MySQL.

src/main/java/database/PgDatabaseConfig.java

@@ -0,0 +1,30 @@
+package database;
+
+import java.time.Duration;
+
+public record PgDatabaseConfig(
+        String databaseName, String host, String schema,
+        String adminUsername, String adminPassword,
+        String username, String password,
+        Duration poolInitTimeout
+) {
+    public PgDatabaseConfig {
+        verifyNotBlank(databaseName);
+        verifyNotBlank(host);
+        verifyNotBlank(schema);
+        verifyNotBlank(adminUsername);
+        verifyNotBlank(adminPassword);
+        verifyNotBlank(username);
+        verifyNotBlank(password);
+    }
+
+    private void verifyNotBlank(String value) {
+        if (value == null || value.isBlank()) {
+            throw new IllegalArgumentException("Missing or blank value in PG database config");
+        }
+    }
+
+    public String getJdbcUrl() {
+        return "jdbc:postgresql://%s:5432/%s".formatted(host, databaseName);
+    }
+}

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();
+    }
+}