public Mono<Void> tryDeleteTwoSidedRelationships(
            @NotNull Long requesterId,
            @NotNull Long relatedUserId,
            @Nullable Integer groupId) {
        try {
            Validator.notNull(requesterId, "requesterId");
            Validator.notNull(relatedUserId, "relatedUserId");
        } catch (ResponseException e) {
            return Mono.error(e);
        }
        return userRelationshipRepository.inTransaction(
                session -> deleteOneSidedRelationship(requesterId, relatedUserId, groupId, session)
                        .flatMap(deleted -> {
                            if (!deleted) {
                                // If not deleted, meaning the relationship between the requester,
                                // and the related user didn't exist, or still exists,
                                // we don't delete the relationship between
                                // the related user and the requester for these cases.
                                return Mono.empty();
                            }
                            return isBlocked(relatedUserId, requesterId, false)
                                    .flatMap(isBlocked -> {
                                        if (isBlocked) {
                                            return Mono.empty();
                                        }
                                        return deleteOneSidedRelationship(relatedUserId,
                                                requesterId,
                                                groupId,
                                                session);
                                    });
                        })
                        .then())
                .retryWhen(TRANSACTION_RETRY);
    }
@return true if the relationship existed and has been deleted;
        <p>
        false if the relationship does not exist, or still exists and has been deleted from a
        relationship group.
turms-service/src/main/java/im/turms/service/domain/user/service/UserRelationshipService.java