Merge #591: Readme: Add mempool flake

bf8de67 README: add mempool extension module (Erik Arvstedt)
c12ff62 README: add some module descriptions (Erik Arvstedt)
2c3fa63 dev/features: improve `enter_service` (Erik Arvstedt)

Pull request description:

ACKs for top commit:
  jonasnick:
    ACK bf8de67

Tree-SHA512: 6bda4aa87656e60bac8bf7acb1831984935602ea599e9e3244cca18f1cf5b4d97ccd9918e12145990a374292af5dda5ad35ecae87596860102f61cf9e6401854

README.md

@@ -88,18 +88,24 @@ NixOS modules ([src](modules/modules.nix))
   * [lndconnect](https://github.com/LN-Zap/lndconnect): connect your wallet to lnd or clightning via a REST onion service
   * [Ride The Lightning](https://github.com/Ride-The-Lightning/RTL): web interface for `lnd` and `clightning`
   * [spark-wallet](https://github.com/shesek/spark-wallet)
-  * [electrs](https://github.com/romanz/electrs)
-  * [fulcrum](https://github.com/cculianu/Fulcrum) (see [the module](modules/fulcrum.nix) for a comparison to electrs)
+  * [electrs](https://github.com/romanz/electrs): Electrum server
+  * [fulcrum](https://github.com/cculianu/Fulcrum): Electrum server (see [the module](modules/fulcrum.nix) for a comparison with electrs)
   * [btcpayserver](https://github.com/btcpayserver/btcpayserver)
-  * [liquid](https://github.com/elementsproject/elements)
+  * [liquid](https://github.com/elementsproject/elements): federated sidechain
   * [JoinMarket](https://github.com/joinmarket-org/joinmarket-clientserver)
     * [JoinMarket Orderbook Watcher](https://github.com/JoinMarket-Org/joinmarket-clientserver/blob/master/docs/orderbook.md)
   * [bitcoin-core-hwi](https://github.com/bitcoin-core/HWI)
 * Helper
   * [netns-isolation](modules/netns-isolation.nix): isolates applications on the network-level via network namespaces
   * [nodeinfo](modules/nodeinfo.nix): script which prints info about the node's services
   * [backups](modules/backups.nix): duplicity backups of all your node's important files
-  * [operator](modules/operator.nix): adds non-root user `operator` who has access to client tools (e.g. `bitcoin-cli`, `lightning-cli`)
+  * [operator](modules/operator.nix): configures a non-root user who has access to client tools (e.g. `bitcoin-cli`, `lightning-cli`)
+
+### Extension modules
+Extension modules are maintained in separate repositories and have their own review
+and release process.
+
+* [Mempool](https://github.com/fort-nix/nix-bitcoin-mempool): Bitcoin visualizer, explorer and API service
 
 Security
 ---

dev/dev-features.sh

@@ -56,9 +56,10 @@ ls -al /var/lib/containers/nb-test
 # Start a shell in the context of a service process.
 # Must be run inside the container (enter with cmd `c`).
 enter_service() {
-    local name=$1
-    nsenter --all -t "$(systemctl show -p MainPID --value "$name")" \
-      --setuid "$(id -u "$name")" --setgid "$(id -g "$name")" bash
+    name=$1
+    pid=$(systemctl show -p MainPID --value "$name")
+    IFS=- read -r uid gid  < <(stat -c "%u-%g" "/proc/$pid")
+    nsenter --all -t "$pid" --setuid "$uid" --setgid "$gid" bash
 }
 enter_service clightning