[slurm-users] Make a job pending in the plugin

Hello all,

I am tyring to build a custom plugin to force some jobs to be pended.

In the official document, `ESLURM*` errors are only valid for `job_submit_lua`.

I tried to send `ESLURM_JOB_PENDING`, but it only rejects the job submission.

Does anyone know how to pend a job in job_submit plugin?

Thanks.