InputBlobTrigger doesn't exist for fresh deployment event subscription

[JimCircadian]

Unlike with deploying the docker image for forecast-processor, the processor function does not exist until deployed separately. Look at hooking the subscription into a dummy function.

Error: waiting for creation/update of System Topic Event Subscription: (Event Subscription Name "sub-proc-icenet-data-topic" / System Topic Name "egs-icenet-data-topic" / Resource Group "rg-icenet-data"): Code="Endpoint validation" Message="Destination endpoint not found. Resource details: resourceId: /subscriptions/REDACTED/resourceGroups/rg-icenetuat-processing/providers/Microsoft.Web/sites/app-icenet-processing/functions/InputBlobTrigger. Resource should pre-exist before attempting this operation.

Need to think of a better manner by which to placeholder the trigger function

Originally posted by @JimCircadian in #43 (comment)