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/docs/output/03-flyway-out-of-order.txt

@@ -0,0 +1,29 @@
+==============================================================================
+Flyway: a lower-versioned migration lands after a higher one is already applied
+==============================================================================
+captured: 2026-09-15T07:07:28.552801366Z
+
+
+-- first startup — V1 and V3 only --
+applied: V1, V3
+
+-- second startup — outOfOrder=false (Flyway default) --
+context failed to start: FlywayValidateException: Validate failed: Migrations have failed validation
+Detected resolved migration not applied to database: 2.
+To ignore this migration, set -ignoreMigrationPatterns='*:ignored'. To allow executing this migration, set -outOfOrder=true.
+Need more flexibility with validation rules? Learn more: https://help.red-gate.com/help/flyway-cli12/help_4.aspx?topic=flyway-blog/older-posts/customize-validation-rules-with-ignoremigrationpatterns
+installed_rank | version | description                               | success
+---------------+---------+-------------------------------------------+--------
+-1             | NULL    | << Flyway Schema History table created >> | true   
+1              | 1       | init                                      | true   
+2              | 3       | add note index                            | true   
+(3 rows)
+
+-- third startup — outOfOrder=true --
+installed_rank | version | description                               | success
+---------------+---------+-------------------------------------------+--------
+-1             | NULL    | << Flyway Schema History table created >> | true   
+1              | 1       | init                                      | true   
+2              | 3       | add note index                            | true   
+3              | 2       | add note length check                     | true   
+(4 rows)