Implement method to drop global prefixes for internal usage when necessary

[ronaldtse]

Some SDOs when citing documents of their own organization, prefers to drop the global prefix on the citation.

For example,

• NIST documents drop the "NIST" prefix, e.g. "NIST SP 800-113" becomes "SP 800-113".
• IETF Internet-Drafts drop the "IETF" prefix, e.g. "IETF Internet-Draft draft-xxx-yyy" becomes "Internet-Draft draft-xxx-yyy")
• BIPM documents drop the "BIPM" prefix, e.g. "BIPM SI Brochure" becomes "SI Brochure"

Relaton shall implement a method to provide the internal use version of an identifier (e.g. for "NIST SP 800-113", the "internal identifier" strips the "NIST"; but for "ISO/IEC 8601", the "internal identifier" is identical to the external one).

The specific flavors affected are as follows:

• "IETF Internet-Draft" or "IETF I-D" (drop "IETF")
• "NIST xxx" or "NBS xxx" (drop "NIST" or "NBS")
• "BIPM xxx" (drop "BIPM")
• "BSI PD", "BSI PAS" (drop "BSI")

This also means that Relaton must guarantee that the PubIDs provided in data includes the full prefix for external use.

i.e.

• NIST identifiers must contain the NIST prefix
• BIPM everything other than CPGM/CIPM (e.g. CCQM) must contain the BIPM prefix
• BSI identifiers must contain the BSI prefix

This can be implemented as:

Relaton.fetch("ISO 8601").identifier(:internal)
=> "ISO 8601"
Relaton.fetch("NIST SP 800-113").identifier
=> "NIST SP 800-113"
Relaton.fetch("NIST SP 800-113").identifier(:internal)
=> "SP 800-113"

This task is dependent on https://github.com/relaton/relaton/issues/103

[andrew2net]

@ronaldtse shouldn't it be implemented in PubId project?