flux-config-kvs(5): add new man page

Problem: No documentation for the new [kvs] config options
exists.

Add man page.

doc/Makefile.am

@@ -292,7 +292,8 @@ MAN5_FILES_PRIMARY = \
 	man5/flux-config-resource.5 \
 	man5/flux-config-archive.5 \
 	man5/flux-config-job-manager.5 \
-	man5/flux-config-ingest.5 
+	man5/flux-config-ingest.5 \
+	man5/flux-config-kvs.5
 
 
 MAN7_FILES = $(MAN7_FILES_PRIMARY)

doc/man5/flux-config-kvs.rst

@@ -0,0 +1,46 @@
+==================
+flux-config-kvs(5)
+==================
+
+
+DESCRIPTION
+===========
+
+The Flux system instance **kvs** service provides the primary key value
+store (i.e. "the KVS") for a large number of Flux services.  For
+example, job eventlogs are stored in the KVS.
+
+The ``kvs`` table may contain the following keys:
+
+
+KEYS
+====
+
+sync
+   (optional) The maximum length of time a change to the primary KVS
+   will stay in memory before it is flushed and the reference is
+   checkpointed.  This used to protect against data loss in the event
+   of a Flux broker crash.
+
+
+EXAMPLE
+=======
+
+::
+
+   [kvs]
+   sync = "30m"
+
+
+RESOURCES
+=========
+
+Flux: http://flux-framework.org
+
+RFC 23: Flux Standard Duration: https://flux-framework.readthedocs.io/projects/flux-rfc/en/latest/spec_23.html
+
+
+SEE ALSO
+========
+
+:man5:`flux-config`

doc/man5/flux-config.rst

@@ -77,4 +77,4 @@ SEE ALSO
 :man1:`flux-broker`, :man5:`flux-config-access`, :man5:`flux-config-bootstrap`,
 :man5:`flux-config-tbon`, :man5:`flux-config-exec`, :man5:`flux-config-ingest`,
 :man5:`flux-config-resource`, :man5:`flux-config-archive`,
-:man5:`flux-config-job-manager`
+:man5:`flux-config-job-manager`, :man5:`flux-config-kvs`

doc/manpages.py

@@ -282,6 +282,7 @@
     ('man5/flux-config-resource', 'flux-config-resource', 'configure Flux resource service', [author], 5),
     ('man5/flux-config-archive', 'flux-config-archive', 'configure Flux job archival service', [author], 5),
     ('man5/flux-config-job-manager', 'flux-config-job-manager', 'configure Flux job manager service', [author], 5),
+    ('man5/flux-config-kvs', 'flux-config-kvs', 'configure Flux kvs service', [author], 5),
     ('man7/flux-broker-attributes', 'flux-broker-attributes', 'overview Flux broker attributes', [author], 7),
     ('man7/flux-jobtap-plugins', 'flux-jobtap-plugins', 'overview Flux jobtap plugin API', [author], 7),
 ]

doc/test/spell.en.pws

@@ -629,3 +629,4 @@ tmpfiles
 EDEADLOCK
 setpgrp
 nosetpgrp
+checkpointed