groupware: refactoring for pagination and support for multiple query suppliers

* refactor APIs in JMAP and Groupware in order to implement pagination
   across multiple accountIds and multiple suppliers (currently
   implemented using a mock supplier for contacts)

 * requires go 1.26 due to use of self-reflecting generics type
   constraints

 * still missing: query criteria and sorting parameters

 * still missing: multi-accountId support for emails

 * errors are now all just 'error' in the APIs, instead of the
   specialized implementations, and are interpreted dynamically where
   necessary in order to transform them into HTTP responses

 * remove position, anchor, anchorOffset as individual query parameters
   as we now only support a 'next=...' token for subsequent pages
   (except in emails for now), and use jmap.QueryParams instead; those
   tokens have a header character for the format, followed by a JSON
   encoded QueryParams map, all wrapped into base62 to make it clearer
   that it is meant to be an opaque token, and not a parameter clients
   should tinker with or construct themselves

 * introduce QueryParamsSupplier as an interface to provide QueryParams
   for various scenarios (single supplier, multiple supplier, ...) per
   accountId

 * implement multi-supplier template methods slist and squery

pkg/jmap/api_objects.go

@@ -27,7 +27,7 @@ func (j *Client) GetObjects(accountId string, //NOSONAR
 	quotaIds []string, identityIds []string,
 	emailSubmissionIds []string,
 	ctx Context,
-) (Result[Objects], Error) {
+) (Result[Objects], error) {
 	l := j.logger("GetObjects", ctx).With()
 	if len(mailboxIds) > 0 {
 		l = l.Array("mailboxIds", log.SafeStringArray(mailboxIds))