Previously, if an application used JPA and declared its own Flyway bean,
startup would fail. The custom Flyway bean would switch off
auto-configuration of the FlywayMigrationInitializer bean but the
context’s entity manager factory beans would still be configured to
depend on the migration initialiser.
This commit splits the post-processor that configures the dependencies
into two. One that configures the dependency on the Flyway bean and
one that configures the dependency on the FlywayMigrationInitializer
bean. When to auto-configuration of the FlywayMigrationInitializer is
switched off, the auto-configuration of the latter dependency is also
switched off.
Closes gh-4079
fd53cbf2f3