Add db-migrations-flyway-liquibase: Flyway vs Liquibase migrations, rollbacks and baselines on Spring Boot 4.1

Companion code for the Flyway vs Liquibase article: checksum validation, out-of-order
and repeatable migrations, baselining an existing schema, Flyway Community's undo/diff/deploy
stubs, concurrent-startup locking for both tools, Liquibase changeset identity and rollback
(auto-generated vs explicit), a verified Liquibase 5.0.3 filename-caching defect, the new
OSS license service, the FSL license change, and running both tools against one database.

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Q6XdRjtsp4862EM44T7i9a

db-migrations-flyway-liquibase/src/main/resources/db/migration/V1__create_customer.sql

@@ -0,0 +1,5 @@
+create table customer (
+    id bigint generated by default as identity primary key,
+    name varchar(120) not null,
+    email varchar(200) not null unique
+);

db-migrations-flyway-liquibase/src/main/resources/db/migration/V2__seed_customer.sql

@@ -0,0 +1,2 @@
+insert into customer (name, email) values ('Ada Lovelace', '[email protected]');
+insert into customer (name, email) values ('Grace Hopper', '[email protected]');