Implement rfc 5545 3.1 content lines length limit

[andrewbrereton]

https://datatracker.ietf.org/doc/html/rfc5545#section-3.1

Lines of text SHOULD NOT be longer than 75 octets, excluding the line break. Long content lines SHOULD be split into a multiple line representations using a line "folding" technique. That is, a long line can be split between any two characters by inserting a CRLF immediately followed by a single linear white-space character (i.e., SPACE or HTAB). Any sequence of CRLF followed immediately by a single linear white-space character is ignored (i.e., removed) when processing the content type.

For example, the line:

DESCRIPTION:This is a long description that exists on a long line.

Can be represented as:

DESCRIPTION:This is a lo
 ng description
  that exists on a long line.