Add documentation to AEAD Algorithms

pgpainless-core/src/main/kotlin/org/pgpainless/algorithm/AEADAlgorithm.kt

@@ -5,8 +5,25 @@
 package org.pgpainless.algorithm
 
 enum class AEADAlgorithm(val algorithmId: Int, val ivLength: Int, val tagLength: Int) {
+
+    /**
+     * Encrypt-then-Authenticate-then-Translate mode.
+     * https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-13.html#name-eax-mode
+     */
     EAX(1, 16, 16),
+
+    /**
+     * Offset-Codebook mode. OCB is mandatory to implement in crypto-refresh. Favored by GnuPG. Is
+     * not yet FIPS compliant, but supported by most implementations and therefore favorable.
+     * https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-13.html#name-ocb-mode
+     */
     OCB(2, 15, 16),
+
+    /**
+     * Galois/Counter-Mode. GCM is controversial. Some say it is hard to get right. Some
+     * implementations like GnuPG therefore avoid it. May be necessary to achieve FIPS compliance.
+     * https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-13.html#name-gcm-mode
+     */
     GCM(3, 12, 16),
     ;