Add read only database configuration/builder option

When using DatabaseBuilder.readOnlyDatabase(true) then
ebean will:
- Set the DataSourceBuilder to use autoCommit=true and readOnly=true
- Use the same DataSource instance for both dataSource and readOnlyDataSource

This is to simplify the setup/configuration for creating a Database that
will only have read-only use.

Note that readOnly=true is a JDBC hint and for example H2 database effectively
ignores that hint where as Postgres will enforce the read-only true nature.

ebean-test/src/test/java/org/tests/readonly/PostgresReadOnlyDatabaseTest.java

@@ -0,0 +1,119 @@
+package org.tests.readonly;
+
+import io.ebean.Database;
+import io.ebean.DatabaseBuilder;
+import io.ebean.Transaction;
+import io.ebean.annotation.Transactional;
+import io.ebean.datasource.DataSourceBuilder;
+import io.ebean.test.containers.PostgresContainer;
+import io.ebeaninternal.api.SpiTransaction;
+import jakarta.persistence.PersistenceException;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+import org.tests.model.basic.UTDetail;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+class PostgresReadOnlyDatabaseTest {
+
+  private static Database readDb;
+
+  @BeforeAll
+  static void beforeAll() {
+    readDb = setupReadOnlyDatabase();
+  }
+
+  @Test
+  void insertPreventedInReadOnlyTransaction() {
+    assertThatThrownBy(() -> {
+      try (Transaction transaction = readDb.beginTransaction()) {
+        UTDetail u0 = new UTDetail("u0", 45, 3D);
+        readDb.save(u0);
+      }
+    }).isInstanceOf(PersistenceException.class)
+      .hasMessageContaining("ERROR: cannot execute INSERT in a read-only transaction");
+  }
+
+  @Test
+  void queryInExplicitTransaction() {
+    try (Transaction transaction = readDb.beginTransaction()) {
+      List<UTDetail> list = readDb.find(UTDetail.class).findList();
+      assertThat(list).hasSize(2);
+      assertThat(transaction.isReadOnly()).isTrue();
+      transaction.commit(); // autoCommit=true but this is still allowed
+    }
+  }
+
+  @Test
+  void queryInImplicitTransaction() {
+    List<UTDetail> list = readDb.find(UTDetail.class).findList();
+    assertThat(list).hasSize(2);
+  }
+
+  // Requires .register(true).defaultDatabase(true) ... when running this test
+  @Disabled
+  @Test
+  void queryInReadOnlyTransactional() {
+    readOnlyTransactional();
+    transactionalOnlyContainingQueries();
+  }
+
+  @Transactional(readOnly = true)
+  void readOnlyTransactional() {
+    List<UTDetail> list = readDb.find(UTDetail.class).findList();
+    assertThat(list).hasSize(2);
+
+    SpiTransaction current = (SpiTransaction) Transaction.current();
+    assertThat(current.isReadOnly()).isTrue();
+  }
+
+  @Transactional
+  void transactionalOnlyContainingQueries() {
+    List<UTDetail> list = readDb.find(UTDetail.class).findList();
+    assertThat(list).hasSize(2);
+
+    SpiTransaction current = (SpiTransaction) Transaction.current();
+    assertThat(current.isReadOnly()).isTrue();
+  }
+
+  private static Database setupReadOnlyDatabase() {
+    PostgresContainer.builder("15")
+      .dbName("readonly_test")
+      .build()
+      .start();
+
+    var dataSourceBuilder = DataSourceBuilder.create()
+      .username("readonly_test")
+      .password("test")
+      .url("jdbc:postgresql://localhost:6432/readonly_test");
+
+    var writeDb = databaseBuilder(dataSourceBuilder)
+      .ddlGenerate(true)
+      .ddlRun(true)
+      .build();
+
+    writeDb.truncate(UTDetail.class);
+    writeDb.save(new UTDetail("u0", 45, 3D));
+    writeDb.save(new UTDetail("u1", 42, 5D));
+
+    return databaseBuilder(dataSourceBuilder)
+      .readOnlyDatabase(true)
+      // register + default required for the tests using @Transactional
+      // .register(true).defaultDatabase(true)
+      .build();
+  }
+
+  private static DatabaseBuilder databaseBuilder(DataSourceBuilder dataSourceBuilder) {
+    return Database.builder()
+      .name("ro_test")
+      .dataSourceBuilder(dataSourceBuilder)
+      .ddlExtra(false)
+      .defaultDatabase(false)
+      .register(false)
+      .addClass(UTDetail.class);
+  }
+}