DataSourceBuilder cannot derive a DataSource from a lazy connection proxy

[vpavic]

While attempting to use newly introduced spring.datasource.connection-fetch=lazy in a project that uses separate JDBC credentials for running Liquibase migrations I came across the issue with the following root cause:

 Caused by: org.springframework.boot.jdbc.UnsupportedDataSourcePropertyException: Unable to find suitable method for url
 	at org.springframework.boot.jdbc.UnsupportedDataSourcePropertyException.throwIf(UnsupportedDataSourcePropertyException.java:36)
 	at org.springframework.boot.jdbc.DataSourceBuilder$ReflectionDataSourceProperties.getMethod(DataSourceBuilder.java:605)
 	at org.springframework.boot.jdbc.DataSourceBuilder$ReflectionDataSourceProperties.get(DataSourceBuilder.java:595)
 	at org.springframework.boot.jdbc.DataSourceBuilder.build(DataSourceBuilder.java:186)
 	at org.springframework.boot.liquibase.autoconfigure.LiquibaseAutoConfiguration$LiquibaseConfiguration.getMigrationDataSource(LiquibaseAutoConfiguration.java:173)
 	at org.springframework.boot.liquibase.autoconfigure.LiquibaseAutoConfiguration$LiquibaseConfiguration.createSpringLiquibase(LiquibaseAutoConfiguration.java:148)
 	at org.springframework.boot.liquibase.autoconfigure.LiquibaseAutoConfiguration$LiquibaseConfiguration.liquibase(LiquibaseAutoConfiguration.java:105)
 	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
 	at java.base/java.lang.reflect.Method.invoke(Method.java:565)
 	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.lambda$instantiate$0(SimpleInstantiationStrategy.java:155)
 	... 124 more

The exact scenario that led to this can be reproduced using LiquibaseAutoConfigurationTests#lazyConnectionDataSource test from the first commit in this PR.

At quick glance it seems the same issue can happen with Flyway and Spring Boot's database initialization and looks like a limitation of DataSourceBuilder and its support for deriving a builder from existing data sources which second commit in this PR attempts to address.