Review casing of keywords

fapi-grant-management.md line 89 (where it says the authorization server shall handle the grant) uses shall in lower-case. That and other parts of the document should be reviewed to see if the proper casing of the keywords are being used.

NOTE: The preamble makes reference to BCP14, RFC2119, and RFC8174 where it says that only when these keywords are in all capitals shall they be considered special.