Set `mydevices` to true by default
Set `mydevices` to true by default

- privates webhook from being triggered by events from public firehose
- see: https://github.com/spark/docs/issues/64

Signed-off-by: Kenneth Lim <9e44d7eb6fcab62e2399c89db54e6ef42f0711a1@gmail.com>

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