Implement Deref<Target=UrlClient> for EsploraBlockchain

There is currently no way to access the client
from the EsploraBlockchain. This makes it difficult
for users to extend it's functionality. This PR exposes
both the reqwest and ureq clients. This PR is related to
PR bitcoindevkit#705.

Author: vladimirfomene

src/blockchain/esplora/reqwest.rs

@@ -46,7 +46,8 @@ struct UrlClient {
 /// See the [`blockchain::esplora`](crate::blockchain::esplora) module for a usage example.
 #[derive(Debug)]
 pub struct EsploraBlockchain {
-    url_client: UrlClient,
+    /// Esplora reqwest client
+    pub url_client: UrlClient,
     stop_gap: usize,
 }
 
@@ -101,6 +102,14 @@ impl Blockchain for EsploraBlockchain {
     }
 }
 
+impl Deref for EsploraBlockchain {
+    type Target = UrlClient;
+
+    fn deref(&self) -> &Self::Target {
+        &self.url_client
+    }
+}
+
 impl StatelessBlockchain for EsploraBlockchain {}
 
 #[maybe_async]

src/blockchain/esplora/ureq.rs

@@ -45,7 +45,8 @@ struct UrlClient {
 /// See the [`blockchain::esplora`](crate::blockchain::esplora) module for a usage example.
 #[derive(Debug)]
 pub struct EsploraBlockchain {
-    url_client: UrlClient,
+    /// Esplora ureq client
+    pub url_client: UrlClient,
     stop_gap: usize,
     concurrency: u8,
 }
@@ -98,6 +99,14 @@ impl Blockchain for EsploraBlockchain {
     }
 }
 
+impl Deref for EsploraBlockchain {
+    type Target = UrlClient;
+
+    fn deref(&self) -> &Self::Target {
+        &self.url_client
+    }
+}
+
 impl StatelessBlockchain for EsploraBlockchain {}
 
 impl GetHeight for EsploraBlockchain {