Update the structs and add comments for cardinality

Signed-off-by: Vlad Velici <vlad.velici@gmail.com>
Tag format parser tests and initial version of parser

Signed-off-by: Vlad Velici <vlad.velici@gmail.com>
Tag parser tests pass and 100% coverage

Signed-off-by: Vlad Velici <vlad.velici@gmail.com>