Set Bouncy Castle as optional feature in Gradle build

- Added bouncyCastle feature for marking Bouncy Castle libraries as optional

Author: exceptionfactory

build.gradle

@@ -49,11 +49,19 @@ configurations.implementation.transitive = false
 def bouncycastleVersion = "1.80"
 def sshdVersion = "2.15.0"
 
+java {
+    withJavadocJar()
+    withSourcesJar()
+    registerFeature('bouncyCastle') {
+        usingSourceSet(sourceSets.main)
+    }
+}
+
 dependencies {
   implementation "org.slf4j:slf4j-api:2.0.17"
-  implementation "org.bouncycastle:bcprov-jdk18on:$bouncycastleVersion"
-  implementation "org.bouncycastle:bcpkix-jdk18on:$bouncycastleVersion"
   implementation "com.hierynomus:asn-one:0.6.0"
+  bouncyCastleImplementation "org.bouncycastle:bcprov-jdk18on:$bouncycastleVersion"
+  bouncyCastleImplementation "org.bouncycastle:bcpkix-jdk18on:$bouncycastleVersion"
 }
 
 license {
@@ -68,11 +76,6 @@ license {
   ])
 }
 
-java {
-	withJavadocJar()
-	withSourcesJar()
-}
-
 if (!JavaVersion.current().isJava9Compatible()) {
   throw new GradleScriptException("Minimum compilation version is Java 9")
 }
@@ -98,6 +101,8 @@ testing {
         implementation "org.apache.sshd:sshd-sftp:$sshdVersion"
         implementation "org.apache.sshd:sshd-scp:$sshdVersion"
         implementation "ch.qos.logback:logback-classic:1.5.18"
+        implementation "org.bouncycastle:bcprov-jdk18on:$bouncycastleVersion"
+        implementation "org.bouncycastle:bcpkix-jdk18on:$bouncycastleVersion"
       }
 
       targets {