path unit: add TriggerLimitBurst= and TriggerLimitIntervalSec=

Given there's now a default for these settings, also allow users to configure
them, matching socket units

man/systemd.path.xml

@@ -186,6 +186,21 @@
         in question. Takes an access mode in octal notation. Defaults
         to <option>0755</option>.</para></listitem>
       </varlistentry>
+      <varlistentry>
+        <term><varname>TriggerLimitIntervalSec=</varname></term>
+        <term><varname>TriggerLimitBurst=</varname></term>
+
+        <listitem><para>Configures a limit on how often this path unit may be activated within a specific time
+        interval. The <varname>TriggerLimitIntervalSec=</varname> may be used to configure the length of the time
+        interval in the usual time units <literal>us</literal>, <literal>ms</literal>, <literal>s</literal>,
+        <literal>min</literal>, <literal>h</literal>, … and defaults to 2s (See
+        <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry> for details on
+        the various time units understood). The <varname>TriggerLimitBurst=</varname> setting takes a positive integer
+        value and specifies the number of permitted activations per time interval, and defaults to 200. Set either to
+        0 to disable any form of trigger rate limiting. If the limit is hit, the unit is placed into a failure mode,
+        and will not watch the path(s) anymore until restarted. Note that this limit is enforced before the service
+        activation is enqueued.</para></listitem>
+      </varlistentry>
     </variablelist>
 
     <xi:include href="systemd.service.xml" xpointer="shared-unit-options" />