Expose additional TLS backends for electrum-client via features

Recently, `rustls` introduced a new default crypto provider in
`aws-lc-rc`. Since there have been reports on this new provider not
building properly on certain platforms `electrum-client` introduced
additional features allowing the user to configure what backend to use
for TLS.

Here, we simply re-expose these features to our users, which also
mirrors what we do for Esplora already.

Author: tnull

ci/ci-tx-sync-tests.sh

@@ -24,6 +24,9 @@ cargo check --verbose --color always --features esplora-blocking
 cargo check --verbose --color always --features esplora-async
 cargo check --verbose --color always --features esplora-async-https
 cargo check --verbose --color always --features electrum
+cargo check --verbose --color always --features electrum-rustls
+cargo check --verbose --color always --features electrum-rustls-ring
+cargo check --verbose --color always --features electrum-openssl
 
 if [ -z "$CI_ENV" ] && [[ -z "$BITCOIND_EXE" || -z "$ELECTRS_EXE" ]]; then
 	echo -e "\n\nSkipping testing Transaction Sync Clients due to BITCOIND_EXE or ELECTRS_EXE being unset."
@@ -34,6 +37,9 @@ else
 	cargo test --verbose --color always --features esplora-async
 	cargo test --verbose --color always --features esplora-async-https
 	cargo test --verbose --color always --features electrum
+	cargo test --verbose --color always --features electrum-rustls
+	cargo test --verbose --color always --features electrum-rustls-ring
+	cargo test --verbose --color always --features electrum-openssl
 fi
 
 popd

lightning-transaction-sync/Cargo.toml

@@ -19,7 +19,12 @@ time = []
 esplora-async = ["async-interface", "esplora-client/async", "esplora-client/tokio", "futures"]
 esplora-async-https = ["esplora-async", "esplora-client/async-https-rustls"]
 esplora-blocking = ["esplora-client/blocking"]
-electrum = ["electrum-client"]
+
+# Default to `rustls`
+electrum = ["electrum-rustls"]
+electrum-rustls = ["electrum-client/use-rustls"]
+electrum-rustls-ring = ["electrum-client/use-rustls-ring"]
+electrum-openssl = ["electrum-client/use-openssl"]
 async-interface = []
 
 [dependencies]
@@ -28,7 +33,10 @@ lightning-macros = { version = "0.1", path = "../lightning-macros", default-feat
 bitcoin = { version = "0.32.2", default-features = false }
 futures = { version = "0.3", optional = true }
 esplora-client = { version = "0.11", default-features = false, optional = true }
-electrum-client = { version = "0.22.0", optional = true }
+
+# As of v0.22, electrum-client's `proxy` feature is still defacto mandatory,
+# see https://github.com/bitcoindevkit/rust-electrum-client/issues/91
+electrum-client = { version = "0.22.0", optional = true, default-features = false, features = ["proxy"] }
 
 [dev-dependencies]
 lightning = { version = "0.2.0", path = "../lightning", default-features = false, features = ["std", "_test_utils"] }