doc: document new content-sqlite config

Problem: The new journal_mode, synchronous, and preallocate configs
for the content-sqlite module are not documented.

Add them in new doc/man5/flux-config-content-sqlite.rst.

doc/Makefile.am

@@ -363,7 +363,8 @@ MAN5_FILES_PRIMARY = \
 	man5/flux-config-ingest.5 \
 	man5/flux-config-kvs.5 \
 	man5/flux-config-policy.5 \
-	man5/flux-config-queues.5
+	man5/flux-config-queues.5 \
+	man5/flux-config-content-sqlite.5
 
 
 MAN7_FILES = $(MAN7_FILES_PRIMARY)

doc/man5/flux-config-content-sqlite.rst

@@ -0,0 +1,53 @@
+=============================
+flux-config-content-sqlite(5)
+=============================
+
+
+DESCRIPTION
+===========
+
+The Flux system may configure one of several possible content backends for
+storing data to long term disk.  The ``content-sqlite`` module is one
+such backend, using ``sqlite`` for storage.
+
+The ``content-sqlite`` table may contain the following keys:
+
+
+KEYS
+====
+
+journal_mode
+   (optional) Configure the sqlite journal mode.  By default is set to ``WAL``
+   if a flux statedir is configured, otherwise defaults to ``OFF``.  Legal options
+   are ``DELETE``, ``TRUNCATE``, ``PERSIST``, ``MEMORY``, ``WAL``, and ``OFF``.
+
+synchronous
+   (optional) Configure the sqlite synchronous mode.  By default is set to ``NORMAL``
+   if a flux statedir is configured, otherwise defaults to ``OFF``.  Legal options
+   are ``EXTRA``, ``FULL``, ``NORMAL``, ``OFF``.
+
+preallocate
+   (optional) Specify a number of bytes to preallocate to the sqlite database.  This
+   can ensure the module can continue to function even if the disk has been full
+   due to other operations on the node (e.g. system logging has filled up disk).  Using
+   preallocated space requires journaling to be disabled, which will automatically be
+   done if the disk is out of space and the preallocate setting is configured.
+
+
+EXAMPLES
+========
+
+::
+
+   [content-sqlite]
+   journal_mode = "WAL"
+   synchronous = "NORMAL"
+   preallocate = 10737418240
+
+
+SEE ALSO
+========
+
+:man5:`flux-config`,
+`sqlite <https://www.sqlite.org/>`_,
+`sqlite pragmas <https://www.sqlite.org/pragma.html>`_