Allow non-lowercase qualifier keys

[dwalluck]

The spec says that keys are case insensitive and that the canonical form is lowercase. This means that the parser should accept any case, but treat all variations as the same key.

[dwalluck]

A key is case insensitive. The canonical form is lowercase

This seems to say that keys of any case are allowed, but should be treated as identical.

If the qualifiers are not empty and not composed only of key/value pairs where the value is empty:

Append '?' to the purl
Build a list from all key/value pair:

Discard any pair where the value is empty.

This seems to say that empty values are allowed, but discarded.

This poses a problem for the builder. Should it allow you to add null or "" keys and just have it be a no-op? I think so, so those tests had to be changed. It is the PackageURL constructor which currently does the qualifier cleanup. The builder doesn't contain any validation or cleanup logic.

In any case, you still have some weird behavior since adding entry { "FOO" : "bar" } is legal, but purl.getQualifiers().get("FOO") is null while purl.getQualifiers().get("foo") is "bar".

It's possibly best that a future API just allow something like purl.getQualifier("foO") to always return "bar" (a case insensitive map, essentially).

[ppkarwasz]

Looks almost good to me.

[jeremylong]

@dwalluck mind fixing the merge conflicts on this one? Sorry that we are getting to these late and thus causing so many merge conflicts.

[jeremylong]

LGTM