More information on vignettes regarding how searches are performed

[daniellenewby]

Is your feature request related to a problem? Please describe.
I use the package but i dont know how it performs searches on specific arguments and these should be further documented and described in the vignette.

Describe the solution you'd like
A clear and concise description of what and how the arguments do searches for specific arguments

Describe alternatives you've considered
Asking the maintainer which is not efficient

Additional context
The arguments that need more information regarding the searches are as follows
getCandidateCodes() - how is the search on the keywords done? exact match / fuzzy?
summariseOrphanCodes() - again is this based on fuzzy matching? what tables is it looking at?
summariseUnmappedCodes() - how is this done and where does it look for this information? from the source_concept_id? doesnt it need to be in the concept table?