Metapath sequence cardinality test functions

[david-waltermire]

User Story

As a Metapath author, I need the ability to test the cardinality of a sequence in a Metapath expression.

Goals

Add support for the functions that test the cardinality of sequences:

• fn:zero-or-one Returns $arg if it contains zero or one items. Otherwise, raises an error.
• fn:one-or-more Returns $arg if it contains one or more items. Otherwise, raises an error.
• fn:exactly-one Returns $arg if it contains exactly one item. Otherwise, raises an error.

Dependencies

none

Acceptance Criteria

• All website and readme documentation affected by the changes in this issue have been updated.
• A Pull Request (PR) is submitted that fully addresses the goals of this User Story. This issue is referenced in the PR.
• The CI-CD build process runs without any reported errors on the PR. This can be confirmed by reviewing that all checks have passed in the PR.

Revisions

No response