fix: User (with a capital letter in the username) cannot post to a sp…

…ace from the global stream - MEED-7905 (#4258)

The space member is tokenized and indexed in lowercase. This change will
ensure that the username is passed in lowercase to work around these use
cases.

component/core/src/main/java/org/exoplatform/social/core/space/SpaceListAccess.java

@@ -298,7 +298,7 @@ private SpaceSearchFilter getSpaceSearchFilter() {
             || type == ACCESSIBLE
             || type == VISIBLE
             || statusType != null)) {
-      return new SpaceSearchFilter(username,
+      return new SpaceSearchFilter(username.toLowerCase(),
                                    filter.getIdentityId(),
                                    filter.getTemplateId(),
                                    filter.getManagingTemplateIds(),