Use Java 8 as source and target versions

[pfichtner]

The current JSONDB version only runs under Java 10 because it was compiled with or for Java 10. In fact, there is no reason for this: JSONDB itself does not use Java features greater than 8 and even no dependencies require a higher Java version than 8. So only the source/targets settings prevents the use of JSONDB in environments where Java 8 is set.

[FarooqKhan]

I built and released jsondb with both java8 and java 11

built with java 11.
https://mvnrepository.com/artifact/io.jsondb/jsondb-core/1.0.115-j11

built with java 8
https://mvnrepository.com/artifact/io.jsondb/jsondb-core/1.0.115-j8

[FarooqKhan]

Thankyou for the pull request, but this change worries me a bit about how it impacts everyone else.

[pfichtner]

Thanks for accepting the PR although I don't understand why there are now two versions of jsondb.
The version built with Java8 can be used with every JRE >= 8 since Java is backward compatible. You only have to use higher Java versions if your code uses newer features. Since your project can be built using JDK 8 this clearly indicates, that you are not using any Java features newer than Java 8.
There is no impact for anybody (beside that projects that depend on Java 8,9 can now use jsondb as well).

[FarooqKhan]

@pfichtner I have not merged the PR because I don't see a reason to merge. The current code should compile with Java 8 as well as any later version. If you want to use the library under java 8 you should use the https://mvnrepository.com/artifact/io.jsondb/jsondb-core/1.0.115-j8
This has been available since Mar 2020.

[pfichtner]

@FarooqKhan Oh! Thanks didn't realize that there is a separate version available, thanks for the hint. But what makes me curious is: What's the difference of that two versions (beside that the class files versions differ 52 vs 55), so what's the reason for binary jar jsondb-core-j11?