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Initiating subscriptions by direct request
Rather than having a third party initiate a subscription using an introduction, a A pico can directly request initiate a subscription. In this case, rather than use event:send, the pico would raise the event to itself, The subscription is initiated by a rule installed in the pico raising the wrangler:subscription event in the postlude block of one of its rules.
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As in the case of introductions, the other target pico must have a rule selecting on wrangler/inbound_pending_subscription_added which will complete the subscription process by raising the wrangler/pending_subscription_approval event.
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