Remove dependency on node-stringprep

[maurelian]

It has a lot of build issues: xmppo/node-stringprep#94

[maurelian]

After discussion with @Arachnid based on the following research, we've decided to keep current dependency until it actually causes an issue that forces us to invest the effort required to replaces this.

Nameprep search

Issue

Cannot find a maintained implementation of name prep for the registrar package

Options

1. Use existing libraries:

Search terms used include: stringprep, nameprep, IDN, IDNA, IETF, RFC

• https://www.npmjs.com/package/node-stringprep (Currently in use in the package)
  • not building in certain versions of linux
  • unmaintained
• https://github.com/eloquent/precis-js
  • The PRECIS Framework, otherwise known as RFC 7564 (Not the same as stringprep, it obsoletes stringprep)
• https://www.npmjs.com/package/libidn
  • no one uses it, and it's not hosted on github anymore

2. Reimplement Nameprep

Tables from stringprep

• Repertoire: Unicode3.2
• Mapping: Tables B.1, B.2
• Normalize: Unicode normalization form KC
• Prohibit: Tables C.1.2, C.2.2, C.3, C.4, C.5, C.6, C.7, C.8, C.9
• Check (bidi):This profile specifies checking bidirectional strings as described in
  STRINGPREP section 6

Background:

Stringprep

• Preparing Unicode text strings in order to increase the likelihood that string input and string comparison work in ways that make sense for typical users throughout the world
• Preparation steps:
  • Mapping
  • Normalize
  • Prohibit
  • Check (bidi) Check for bidirectional characters

Nameprep
is the process of case-folding to lowercase and removal of some generally invisible code points before it is suitable to represent a domain name, or other such canonical name. It is used by IDNA, using the Unicode standard for NFKC normalization.

NFKC:
Normalization Form Compatibility Composition Characters are decomposed by compatibility, then recomposed by canonical equivalence.

Internationalized domain names in applications:
An internationalized domain name (IDN) is an Internet domain name that contains at least one label that is displayed in software applications, in whole or in part, in a language-specific script or alphabet, such as Arabic, Chinese, Cyrillic, Tamil, Hebrew or the Latin alphabet-based characters with diacritics or ligatures, such as French. These writing systems are encoded by computers in multi-byte Unicode. Internationalized domain names are stored in the Domain Name System as ASCII strings using Punyc¥ode transcription.

Refs:

• Normalizing examples
• https://github.com/nodejs/node/blob/master/deps/icu-small/source/common/unicode/idna.h