It took me a long time to discover why a base 64 encoded SHA-512 hash was 89 characters long instead of the expected 88. The documentation does not mention that the encode function inserts newlines after 76 characters. Please make a note of this behavior.
Patch submissions are welcomed. Though there is an argument for this being an implementation detail one shouldn't rely upon and therefore should not be described in user-facing documentation.
By the way, this is a very poor design decision.
It seems to be something we inherited some 20 years ago and are not likely to change even though I suspect you will find general agreement with your position. Though since its isn't documented maybe changing it would be ok.
The workaround of trimming whitespace characters from the encoded string is ugly and unacceptable.
It may be a bit ugly but when dealing with base64, specifically when decoding, whitespace of this nature is expressly allowed. Its historical presence here, based upon MIME requirements prevalent at the time the code was written, doesn't alter its meaning and so it somewhat rightfully considered an implementation detail that is not necessary to document.
