in teamcity-invitations-plugin-server/src/main/java/org/jetbrains/teamcity/invitations/InvitationsStorage.java [63:71]
public Invitation addInvitation(@NotNull Invitation invitation) {
Map<String, String> params = invitation.asMap();
params.put(INVITATION_TYPE, invitation.getType().getId());
invitation.getProject().addFeature(PROJECT_FEATURE_TYPE, params);
teamCityCore.persist(invitation.getProject(), "Invitation added");
Loggers.SERVER.info("Invitation " + invitation.describe(false) + " is created in the project " + invitation.getProject().describe(false));
getInvitation(invitation.getToken());//populate cache
return invitation;
}