Support multiple ADE keys on MacOS

[gcarvelli]

This PR is better viewed with whitespace ignored.

Summary

This PR adds support for multiple Adobe Digital Editions decryption keys on MacOS. I found myself with two decryption keys because I:

1. Installed ADE on a new computer
2. Claimed an ascm ebook
3. Signed into my Adobe account
4. Claimed another ascm ebook

I believe this issue is describing the same problem I had.

Testing

This can be tested by adding a new <adept:credentials> block to your ~/Library/Application Support/Adobe/Digital Editions/activation.dat. I do not know how to generate those keys, however.

Let me know if I can do anything else to make this better or to make testing it easier!

[squio]

LGTM 👍 (would have positively reviewed if I had the rights)

[noDRM]

Thanks for the PR. I don't have a MacOS setup to test this.

However, looking at the code, I'm not sure if the code works as intended. When there's multiple authorizations in that XML file, each one of them can have their own username or authorization method.

Your code seems to account for multiple authorizations to be present, but I'm not sure whether the key names / authorization methods will be correctly matched to each key since it's still just using tree.find on the whole XML tree?

Can you check that again to make sure the method and username are correct when there's multiple different ones?