docs(proposals): gRPC outputs goals/non-goals

Co-authored-by: Lorenzo Fontana <lo@linux.com>
Signed-off-by: Leonardo Di Donato <leodidonato@gmail.com>

proposals/20190826-grpc-outputs.md

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+# gRPC Falco Output
+
+<!-- toc -->
+
+## Summary
+
+We intend to build a gRPC interface to allow users receive and consume the alerts regarding the violated rul.
+
+## Motivation
+
+The most valuable information that Falco can give to its users are the alerts.
+An alert is given by Falco each time a rule is matched.
+At the current moment, however, Falco can deliver alerts in a very basic way, for example by dumping
+them to standard output.
+
+For this reason, many Falco users asked, with issues - eg., [falco#528](https://github.com/falcosecurity/falco/issues/528) - or in the [slack channel]() if we can find a more consumable way to
+implement Falco outputs in an extensible way.
+
+The motivation behind this proposal is to design a new output implementation that can meet our user's needs.
+
+### Goals
+
+- To design and implement an additional output containing a gRPC client
+- To keep it as simple as possible
+- To have a simple contract interface
+- To only have the responsibility to route Falco output requests and responses
+- To continue supporting the old output formats by implementing their same interface
+- To be secure by default
+- To be asynchronous and non-blocking
+
+
+### Non-Goals
+
+- To substitute existing outputs (stdout, syslog, etc.)
+- To support connecting to multiple gRPC servers
+  - Users can have a single server multiplexing requests to multiple servers
+- To support queuing mechanisms for message retransmission
+  - Users can have a local gRPC relay server along with Falco that multiplexes connections and handles retires and backoff
+- To change the output format
+- To make the message context (text, fields, etc.) and format configurable
+  - Users can already override rules changing their output messages
+- To act as an orchestrator for Falco instances
+
+
+## Proposal
+
+## Design Details
+
+---