Modify Expert: allow non-string values in extra

[grodriguezl]

Modify expert fails when it tries to add a non-string value to extra.something It cannot format a boolean or integer value.

File "/usr/lib/python3.6/site-packages/intelmq/bots/experts/modify/expert.py", line 97, in apply_action
    event.add(name, value.format(msg=event,
AttributeError: 'int' object has no attribute 'format'

Example of config:

[
  {
    "rulename": "Add extra.rule",
    "if": {
        "source.reverse_dns": "^test.com$"
    },
    "then": {
        "extra.test": 1,
        "extra.test2": true
    }
  }
]

intelmq/intelmq/bots/experts/modify/expert.py

Lines 99 to 102 in 60f1b14

	event.add(name, value.format(msg=event,
	matches={k: MatchGroupMapping(v)
	for (k, v) in matches.items()}),
	overwrite=self.overwrite)