DocumentId doesn't always convert down to String and back

[heckj]

While digging on a flaky test (#104), I resolved that issue only to find that in some cases a DocumentId() generated and converted to a String (DocumentId().id) doesn't 100% of the time convert back to a valid DocumentId().

The code underneath is using BS58 encoding (Base58.base58CheckEncode(data.bytes) for data generated by UUID(). The reverse uses Base58.base58CheckDecode(stringValue) - so you'd think that would be 100%, but apparently not.

An iteration test going through 1000 of these, converting to string and trying to get back, shows a loss of 1 or 2 in 1000 (0.1 to 0.2% failure). Need to figure out why, and in the mean time I have some definite examples:

• 1YNk8bmh2xxuNqeAjsuPy4JjnwF
• 1Tf5GWML5KA18TJqUN9qKarxbhm
• 1ZEbwfpSJxXascTx7sstBecFLky
• 12mS52BJoU16LAzKmMdwgGW4tQQ
• 1kVFyeTJ6WjUmMT8pGCEesQDVxa

[heckj]

XCTAssertNotNil failed - id: 1ezULPhgshBPYi4H2MTBoMKwc3S [00cf851bc4f4441d86d127c26774145e] doesn't back convert (try #71)

XCTAssertNotNil failed - id: 1Ui7LyCmx1vxgvdu2md5t8mcFsC [00975afb316a438ba1b5d9d54d80f113] doesn't back convert (try #293)

[heckj]

Well, that's disappointing. It's a known issue in the upstream project (keefertaylor/Base58Swift#23, keefertaylor/Base58Swift#25), with a PR open to fix it (keefertaylor/Base58Swift#21)

On the plus side, the author appears to still be very active d on GitHub, so hoping that asking about this might get it moving and sorted so that it's an upstream fix we can directly consume.