ENH: more useful table export find func

Summary

1. Add support for passing callable to BaseTableExporter(find_func=callable)
2. Add BaseTableExporter.all_keys.

• Needed for https://git.geomar.de/dm/bis/indiscale/sample-management/-/merge_requests/8

Focus

The magic happens in BaseTableExporter._call_find_function.

Test Environment

Test with geomar setup

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src/caosadvancedtools/table_export.py

@@ -165,7 +165,7 @@ class BaseTableExporter(object):
             elif FIND_FUNCTION in d:
                 if callable(d[FIND_FUNCTION]):
                     find_fun = d[FIND_FUNCTION]
-                else
+                else:
                     find_fun = getattr(self, d[FIND_FUNCTION])
                 try:
                     self.info[e] = find_fun()