Extend the OAuth2 connector so a reconnect can request the union of
previously granted and newly requested scopes without losing either.
Four related changes:
- Connection gains Scopes() []string so callers no longer need a type
switch to reach the scope set. OAuth2Connection and APIKeyConnection
implement it; SlackConnection inherits via embedding.
- OAuth2State carries RequestedScopes and CompleteWithState falls
back to it when the provider omits the scope field (RFC 6749 §5.1
allows this when granted equals requested). Without the fallback
the stored Scope would be empty and the next reconnect would have
no diff base.
- providerDefinition gains SupportsIncrementalAuth, set only for
Google Workspace. When the flag is true and the caller passes
InitiateOptions.IncludeGrantedScopes, the auth URL carries
include_granted_scopes=true and the prompt=consent param is
dropped so reuse flows see only the delta consent screen.
- InitiateOptions gains ConnectorID so the reconnect case is passed
explicitly instead of relying on the caller to mutate r.URL.Query.
Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>
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