Validate actual rule object instead of Field#type for @Rule

[vlsi]

fixes #1720

[junit-builds]

JUnit 4 is now in maintenance mode.

At this point, only critical bugs and security issues will be fixed.

The team has therefore decided to close this PR.

[vlsi]

@junit-builds , can you please reconsider?

The issue blocks Testcontainers from dropping junit4 runtime dependency since this specific validation enforces that the field has to be junit4's Rule.

It is extremely annoying that Testcontainers has to bring junit4 dependency even though I do not need it. It is bad it results in multiple @Test annotations on the classpath.

What is your suggestion for testcontainers/testcontainers-java#970 then?

[kcooney]

What is your suggestion for testcontainers/testcontainers-java#970 then?

Multiple suggestions were made in #1720

I think the best approach would be to split testcontainers into multiple libraries, one with the "core" code, and one for each test library that testcontainers supports (see #1720 (comment))