Hide impl package from javadoc (and module declaration)

[Marcono1234]

Describe the problem you'd like to have solved

It appears the impl package contains part of the internal implementation and should not be used by the user.
However, some of its classes are public and there is no indication to the user that they should not be used.

Describe the ideal solution

• Hide the package from javadoc
• Add a package-info.java file documenting that the package is part of the internal implementation and classes inside of it should not be used.
• Don't export the package from the module declaration, see also Add module system support #483. (Ideally in the next major version since it is a breaking change)
• Remove mentions of impl classes from API documentation:
  • NullClaim: Mentioned from
    • Header.getHeaderClaim
    • Payload.getClaim

[lbalmaceda]

Hide the package from javadoc

This would be solved with the changes you proposed for #489.

Add a package-info.java file documenting that the package is part of the internal implementation and classes inside of it should not be used.

If the package is no longer going to be included in the javadocs, we can probably skip this change if the intent is just to hide the impl package.

Remove mentions of impl classes from API documentation:

Good catch! These should also be removed. If you want to take them as well with the same PR that's OK to us.

[Marcono1234]

Add a package-info.java file documenting that the package is part of the internal implementation and classes inside of it should not be used.

If the package is no longer going to be included in the javadocs, we can probably skip this change if the intent is just to hide the impl package.

Maybe it would be useful nonetheless so it is obvious to users browsing the code that the package contains internal implementation details.

[jimmyjames]

Maybe it would be useful nonetheless so it is obvious to users browsing the code that the package contains internal implementation details.

I agree; it's worth adding.

[jimmyjames]

Fixed with #496, shipped in 3.16.0