Fixes the nullability annotations in SimpleMailMessage so the set*(...) methods have their parameters marked as @Nullable.
These method parameters had no annotations and when SimpleMailMessage is used from Kotlin with -Xjsr305=strict enabled, the set*(...) methods were treated as being marked @NonNull. This also meant Kotlin would not see matched pairs of get/set methods as var properties, so calling message.text = "Text" would not compile in Kotlin.
Adds tests in SimpleMailMessageJsr305ComplianceTests.kt that verify the nullability annotations for SimpleMailMessage are correct. This file will actually fail to compile if the nullability annotations are missing, causing the tests to fail.
Also modifies spring-context-support.gradle to force the Kotlin test code to compile with -Xjsr305=strict, enabling the test code to work properly.
Comment From: stgerhardt
Apologies for the force push on my fork - forgot to set my git command line email properly and wanted to fix it.
Comment From: sdeleuze
Merged via fded79d807b7d6b69e01ecc4e241399a438ee220 without the testFunction method. Thanks for the Kotlin tests, but for the sake of consistency and since we intend to introduce later globally null-safety validation during the build, I did not introduce them.