Default Hibernate DDL auto to none with Flyway/Liquibase

This commit adds a strategy interface to specific if a given DataSource
has its schema managed. The Hibernate auto-configuration uses it to set
it to "none" if a mechanism to initialize the DataSource is
found and "create-drop" otherwise.

Both Flyway and Liquibase implements that strategy interface and
register it in the context accordingly.

Closes gh-9262

spring-boot/src/main/java/org/springframework/boot/jdbc/SchemaManagement.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2012-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.jdbc;
+
+/**
+ * An enumeration of the available schema management options.
+ *
+ * @author Stephane Nicoll
+ * @since 2.0.0
+ */
+public enum SchemaManagement {
+
+	/**
+	 * The schema is managed and will be created at the appropriate time.
+	 */
+	MANAGED,
+
+	/**
+	 * The schema is not managed.
+	 */
+	UNMANAGED
+
+}

spring-boot/src/main/java/org/springframework/boot/jdbc/SchemaManagementProvider.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2012-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.jdbc;
+
+import javax.sql.DataSource;
+
+/**
+ * Strategy interface to determine the {@link SchemaManagement} of a {@link DataSource}.
+ *
+ * @author Stephane Nicoll
+ * @since 2.0.0
+ */
+public interface SchemaManagementProvider {
+
+	/**
+	 * Return the {@link SchemaManagement} for the specified {@link DataSource}.
+	 * @param dataSource the dataSource to handle
+	 * @return the {@link SchemaManagement} for the {@link DataSource}.
+	 */
+	SchemaManagement getSchemaManagement(DataSource dataSource);
+
+}