slurmrestd - add description for slurmdb/job

Mention why multiple jobs may be returned here (which differs from
the default sacct query which will filter out older entries).

Bug 11330

NEWS

@@ -45,6 +45,7 @@ documents those changes that are of interest to users and administrators.
     already allocated to another step. Instead, defer the step until the
     requested node(s) become available.
  -- Return error for a step requesting more memory than the allocation has.
+ -- slurmrestd - add description for slurmdb/job endpoint.
 * Changes in Slurm 20.11.7
 ==========================

src/slurmrestd/plugins/openapi/dbv0.0.36/openapi.json

@@ -43,7 +43,8 @@
           "slurm"
         ],
         "operationId": "slurmdbd_get_job",
-	"summary": "Get job info",
+        "summary": "Get job info",
+        "description": "This endpoint may return multiple job entries since job_id is not a unique key - only the tuple (cluster, job_id, start_time) is unique. If the requested job_id is a component of a heterogeneous job all components are returned.",
         "parameters": [
           {
             "name": "job_id",