add rpc server proposal [ci skip]

docs/hidden/adr-003.md

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+# ADR 1: Must an ABCI-app have an RPC server?
+
+## Context
+
+ABCI-server could expose its own RPC-server and act as a proxy to Tendermint.
+
+The idea was for the Tendermint RPC to just be a transparent proxy to the app.
+Clients need to talk to Tendermint for proofs, unless we burden all app devs
+with exposing Tendermint proof stuff. Also seems less complex to lock down one
+server than two, but granted it makes querying a bit more kludgy since it needs
+to be passed as a `Query`. Also, **having a very standard rpc interface means
+the light-client can work with all apps and handle proofs**. The only
+app-specific logic is decoding the binary data to a more readable form (eg.
+json). This is a huge advantage for code-reuse and standardization.
+
+## Decision
+
+We dont expose an RPC server on any of our ABCI-apps.
+
+## Status
+
+accepted
+
+## Consequences
+
+### Positive
+
+- Unified interface for all apps
+
+### Negative
+
+- `Query` interface
+
+### Neutral