[module:vault] secrets should be a list/seq rather than option

[pPanda-beta]

It's a pretty common use case that someone would require more than one secrets, so I would suggest to use a map (same as java field) or at least a Seq[VaultContainer.Secrets] (a better name would be VaultContainer.Secret) instead of Option.

https://github.com/testcontainers/testcontainers-scala/blob/c2331d7cd9152f9679709bd87940edff7bd33fef/modules/vault/src/main/scala/com/dimafeng/testcontainers/VaultContainer.scala#L9