doc: Add documentation for testing

doc/broker/broker_testing.md

@@ -0,0 +1,48 @@
+## Experimental Broker Feature Testing
+
+In order to test the experimental broker feature, a few manual steps are needed. These will soon be replaced with a revision to the integration test to allow it to optionally use the broker feature, but for the moment manual testing is the only option.
+
+To manually test the broker feature, start by building Rosenpass with the broker feature:
+
+```bash
+cd rosenpass
+cargo build --features=experimental_broker_api
+```
+
+Next, generate keys for two parties using the example Rosenpass configuration files
+
+```bash
+PATH="$PWD/target/debug:$PATH" rosenpass gen-keys config-examples/peer-a-config.toml
+PATH="$PWD/target/debug:$PATH" rosenpass gen-keys config-examples/peer-b-config.toml
+```
+
+Now, open a second terminal and run the following in one (not using the broker):
+
+```bash
+PATH="$PWD/target/debug:$PATH" rosenpass exchange-config config-examples/peer-a-config.toml 
+```
+and the following in the other (spawning a broker and communicating with it via socketpair(2)):
+
+```bash
+cd rosenpass
+PATH="$PWD/target/debug:$PATH" rosenpass --psk_broker_spawn exchange-config config-examples/peer-a-config.toml 
+````
+
+You should see the two parties exchange keys, and can view the shared PSK via `wg show`.
+
+In order to test using a Unix socket at a provided path instead, replace the above command with this:
+
+```bash
+PATH="$PWD/target/debug:$PATH" rosenpass --psk_broker_path broker.sock exchange-config config-examples/peer-a-config.toml
+```
+
+Then, in a third terminal, run the following
+
+```bash
+cd rosenpass
+PATH="$PWD/target/debug:$PATH" rosenpass-wireguard-broker-socket-handler --listen-path broker.sock
+```
+
+You should see the two parties exchange keys.
+
+The `--psk_broker_fd` feature can be similarly tested, but would require a separate script providing an open file descriptor to do so.