Document legacy-status of EdDSA and XDH

pgpainless-core/src/main/kotlin/org/pgpainless/key/generation/type/KeyType.kt

@@ -100,8 +100,18 @@ interface KeyType {
 
         @JvmStatic fun ECDSA(curve: EllipticCurve): ECDSA = ECDSA.fromCurve(curve)
 
+        /**
+         * Legacy EdDSA using Ed25519.
+         * For OpenPGP v4 only.
+         */
         @JvmStatic fun EDDSA(curve: EdDSACurve): EdDSA = EdDSA.fromCurve(curve)
 
+        /**
+         * Legacy ECDH using Curve25519.
+         * For OpenPGP v4 only.
+         */
         @JvmStatic fun XDH(curve: XDHSpec): XDH = XDH.fromSpec(curve)
+
+        // TODO: Add crypto-refresh X25519, X448, Ed25519, Ed448
     }
 }

pgpainless-core/src/main/kotlin/org/pgpainless/key/generation/type/eddsa/EdDSA.kt

@@ -8,6 +8,10 @@ import org.bouncycastle.jce.spec.ECNamedCurveGenParameterSpec
 import org.pgpainless.algorithm.PublicKeyAlgorithm
 import org.pgpainless.key.generation.type.KeyType
 
+/**
+ * Legacy EdDSA using Ed25519.
+ * For use with OpenPGP v4 only.
+ */
 class EdDSA private constructor(val curve: EdDSACurve) : KeyType {
     override val name = "EdDSA"
     override val algorithm = PublicKeyAlgorithm.EDDSA

pgpainless-core/src/main/kotlin/org/pgpainless/key/generation/type/xdh/XDH.kt

@@ -8,6 +8,10 @@ import org.bouncycastle.jce.spec.ECNamedCurveGenParameterSpec
 import org.pgpainless.algorithm.PublicKeyAlgorithm
 import org.pgpainless.key.generation.type.KeyType
 
+/**
+ * Legacy ECDH with Curve25519.
+ * For use with OpenPGP v4 only.
+ */
 class XDH private constructor(spec: XDHSpec) : KeyType {
     override val name = "XDH"
     override val algorithm = PublicKeyAlgorithm.ECDH