feat: add problem checks + handler feature

the basic idea is to run nightly checks and send email if problems are
found.  it should also support variations on that theme,
e.g. configuring a check to only run on certain weekdays.

docs/api/wuttjamaican.cli.problems.rst

@@ -0,0 +1,6 @@
+
+``wuttjamaican.cli.problems``
+=============================
+
+.. automodule:: wuttjamaican.cli.problems
+   :members:

docs/api/wuttjamaican.problems.rst

@@ -0,0 +1,6 @@
+
+``wuttjamaican.problems``
+=========================
+
+.. automodule:: wuttjamaican.problems
+   :members:

docs/glossary.rst

@@ -243,6 +243,24 @@ Glossary
      modules etc. which is installed via ``pip``.  See also
      :doc:`narr/install/pkg`.
 
+   problem check
+      This refers to a special "report" which runs (usually) on a
+      nighty basis.  Such a report is only looking for "problems"
+      and if any are found, an email notification is sent.
+
+      Apps can define custom problem checks (based on
+      :class:`~wuttjamaican.problems.ProblemCheck`), which can then be
+      ran via the :term:`problem handler`.
+
+   problem handler
+      The :term:`handler` responsible for finding and reporting on
+      "problems" with the data or system.  Most typically this runs
+      nightly :term:`checks <problem check>` and will send email if
+      problems are found.
+
+      Default handler is
+      :class:`~wuttjamaican.problems.ProblemHandler`.
+
    provider
      Python object which "provides" extra functionality to some
      portion of the :term:`app`.  Similar to a "plugin" concept; see

docs/index.rst

@@ -70,6 +70,7 @@ Contents
    api/wuttjamaican.cli.base
    api/wuttjamaican.cli.make_appdir
    api/wuttjamaican.cli.make_uuid
+   api/wuttjamaican.cli.problems
    api/wuttjamaican.conf
    api/wuttjamaican.db
    api/wuttjamaican.db.conf
@@ -86,6 +87,7 @@ Contents
    api/wuttjamaican.exc
    api/wuttjamaican.install
    api/wuttjamaican.people
+   api/wuttjamaican.problems
    api/wuttjamaican.progress
    api/wuttjamaican.reports
    api/wuttjamaican.testing

docs/narr/cli/builtin.rst

@@ -51,3 +51,15 @@ Print a new universally-unique identifier to standard output.
 Defined in: :mod:`wuttjamaican.cli.make_uuid`
 
 .. program-output:: wutta make-uuid --help
+
+
+.. _wutta-problems:
+
+``wutta problems``
+------------------
+
+Find and report on problems with the data or system.
+
+Defined in: :mod:`wuttjamaican.cli.problems`
+
+.. program-output:: wutta problems --help