import all private keys in file during setup

[tomholub]

But now I'm thinking of this one :) Eventually we'll make KeyUtil.parse throw when it encounters more than one key.

As long as we do have a test for this scenario: // filter out all content except for the first encountered private key (GPGKeychain compatibility) then it's no problem - whenever we change it, we'll bump into the test and resolve it.

Actually, it's not the most ideal as is - if I give it two private keys, I may actually want to import two private keys. But now we're talking about importing more than one key at once, which is a different issue, I'll make a separate ticket for it.

Originally posted by @tomholub in #3216 (comment)

[tomholub]

As we discussed, the goal is that it will not ignore keys that follow the first one, during manual import.

To test:

• input a file that has several openpgp keys in it
• go through setup
• view settings -> additional settings -> check that there are all expected private keys imported

[tomholub]

It will look something like this

    const attachment = new AttachmentUI(() => Promise.resolve({ count: 100, size: 1024 * 1024, size_mb: 1 }));
    attachment.initAttachmentDialog('fineuploader', 'fineuploader_button', {
      attachmentAdded: async file => {
        let prvs: OpenPGP.key.Key[] = [];
        const utf = file.getData().toUtfStr();
        if (utf.includes(PgpArmor.headers('privateKey').begin)) {
          const armoredPrvBlocks = MsgBlockParser.detectBlocks(utf).blocks.filter(b => b.type === 'privateKey');
          for (const block of armoredPrvBlocks) {
            prvs.push(...(await opgp.key.readArmored(block.content.toString())).keys);
          }
        } else {
          prvs = (await opgp.key.read(file.getData())).keys;
        }
        if (prvs.length) {
          /// ...
        } else {
          await Ui.modal.error('Not able to read this key. Make sure it is a valid PGP private key.', false, Ui.testCompatibilityLink);
        }
      }
    });
  }