ParseScopeString, FormatScopeString, UnionScopes and ScopesCover
encapsulate OAuth2 scope-set arithmetic. ParseScopeString accepts
both the RFC 6749 space-separated form and GitHub's comma-separated
non-compliant form in one pass, so callers can stay format-agnostic.
These primitives are the foundation for scope-preserving reconnect:
later commits compute the union of stored and requested scopes so
a reconnect never drops a previously granted scope.
Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>
