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_changes.go

@@ -74,7 +74,7 @@ func (s StateMap) MarshalZerologObject(e *zerolog.Event) {
 
 // Retrieve the changes in any type of objects at once since a given State.
 // @api:tags changes
-func (j *Client) GetChanges(accountId string, stateMap StateMap, maxChanges uint, ctx Context) (Result[ObjectChanges], Error) { //NOSONAR
+func (j *Client) GetChanges(accountId string, stateMap StateMap, maxChanges uint, ctx Context) (Result[ObjectChanges], error) { //NOSONAR
 	logger := log.From(j.logger("GetChanges", ctx).With().Object("state", stateMap).Uint("maxChanges", maxChanges))
 	ctx = ctx.WithLogger(logger)