doc: improve section about checkconf in the plugin tutorial
See for further details and discussion.
@@ -414,6 +414,16 @@ int elektraLineCheckConfig (Key * errorKey, KeySet * conf)
}
```
+The `elektraPluginCheckConf` function is exported via the plugin's contract. The following example demonstrates how to export the `checkconf` function (see chapter [Contract](Contract) for further details):
+
+```c
+keyNew ("system/elektra/modules/" ELEKTRA_PLUGIN_NAME "/exports/checkconf", KEY_FUNC, elektraLineCheckConfig, KEY_END),
+```
+
+Within the `checkconf` function all of the plugin configuration values should be validated.
+Errors should be reported via Elektra's error handling mechanism (see the section about [ELEKTRA_SET_ERROR](`ELEKTRA_SET_ERROR`) for further details).
+If `checkconf` encounters a configuration value, that is not strictly invalid but can not be parsed by the plugin (e.g. a parameter which is not part of the plugin configuration), then a warning should be appended to `errorKey`, using `ELEKTRA_ADD_WARNING`.
+
### `ELEKTRA_PLUGIN_EXPORT`
The last function, one that is always needed in a plugin, is `ELEKTRA_PLUGIN_EXPORT`. This functions is responsible for letting Elektra know that
