[GAZ-328] Migrate message-gateway to Java 21 / Spring Boot 3.4 / Camel 4 / Jakarta

[GiulioRinalduzzi]

Java 21 / Spring Boot 3.4.4 / Camel 4.4.1 / Jakarta EE 10, same recipe as the paymenthub-ee-* connectors: versions come from enforcedPlatform('org.mifos:paymenthub-ee-bom:2.0.0-SNAPSHOT'). Targets dev as requested. cc @tdaly61

Jakarta: only 8 of 79 source files needed it — javax.persistence (25), javax.xml.bind (2), javax.annotation (2). javax.sql.DataSource deliberately stays javax: it is JDK, not Jakarta EE. There is no Spring Security anywhere in this repo, which is normally the hard part of a Spring Boot 3 move.

Hibernate 6: two changes were needed to make the application start.

• AbstractPersistableCustom used GenerationType.AUTO → now IDENTITY. Every table in db/migration declares its id AUTO_INCREMENT, which is what Hibernate 5 produced from AUTO on MySQL; Hibernate 6 turns it into a sequence table instead.
• SmsOutboundMessageRepository.findByIdInAndTenantId took a String while OutboundMessages.tenantId is a Long. Hibernate 6 refuses to build the derived query. The method has no callers — happy to delete it instead if you prefer.

Dependencies

• Flyway 6.4.0 → 10.x, forced by Spring Boot 3.4. Flyway 10 moved per-database support out of core, so flyway-mysql is now a separate dependency. This is the bit that overlaps with @kanishk Singh's postgres work — the swap should be flyway-mysql → flyway-database-postgresql plus the driver, and IDENTITY works on postgres too, so that part needs no further change.
• mysql:mysql-connector-java → com.mysql:mysql-connector-j (BOM managed).
• gson and okhttp are now declared explicitly. Both are imported directly by the code — gson in 8 files, okhttp in JasminSMSProvider and CallbackEventListner — but neither was declared: they only reached the classpath as transitives of com.infobip:infobip-api-java-client. Bumping or dropping an SMS vendor would have broken eight unrelated classes. gson now takes its version from the BOM, which moves it 2.8.9 → 2.11.0 (the old strictly/force pin is gone). okhttp keeps the 2.3.0 it already resolved to, so nothing changes at runtime — but note that is com.squareup.okhttp 2.x from 2015, and moving to okhttp3 is a source change worth its own ticket, especially as Jasmin is the provider you want for the integration test.
• velocity dropped — nothing imports it, but it was quietly supplying commons-lang 2.x (last released 2011) to three helper classes. Declared commons-lang3 directly and switched those three imports.
• retrofit dropped as a declared dependency. To be precise: retrofit 1.9.0 is still on the classpath, pulled in by the InfoBip SDK. Nothing in src/ references it, so only the declaration went away.
• spring-kafka dropped — zero source references and zero configuration.
• Removed the repository URL with a stray quote in it (.../fyn-libs-snapshot'); that JFrog no longer exists either.
• Twilio / InfoBip / Telerivet SDKs keep explicit versions: the BOM does not manage them.

Build, Docker, CI

• Gradle 7.3 → 8.10.2. profile-standalone.gradle and profile-deployable.gradle used jar.baseName / war.baseName, removed in Gradle 8 → archiveBaseName/archiveVersion.
• Dockerfile: openjdk:11 → eclipse-temurin:21-jre, copies app.jar instead of the *.jar glob (which also matched the -plain.jar that has no Main-Class), and now exposes 5009 as well — the Camel REST port, which the delivery-report callbacks need. callbackconfig.port is outbound only, so it stays unexposed.
• CircleCI: openjdk:17-buster-node-browsers-legacy → the shared PHEE template (cimg/openjdk:21.0.6, multi-arch, image name from CIRCLE_PROJECT_*).
• application.yml: dropped spring.jpa.hibernate.use-new-id-generator-mappings, removed in Spring Boot 3.

Not touched, worth flagging

• This repo has no tests at all — there is no src/test directory. Until there is one, CI proves only that it compiles. The Dummy-provider smoke test is the obvious first one to automate.
• Camel has no routes. There is no RouteBuilder in the repo and the startup log says Routes startup (started:0); only CamelContext and Exchange are used, from ZeebeWorkers. So most of the five camel-* dependencies are dead weight. Left alone here, but worth a ticket.
• application.yml has a hard-coded Telerivet API key and project id committed in the clear, and spring.datasource.url is jdbc:mysql:thin://, which is not a valid MySQL JDBC URL. Both pre-existing, but the key probably wants rotating.
• The email path is still unimplemented: sendEmail is abstract on Provider with an empty body in all 7 providers.