feat: introduce methods for transit API interaction (#89)

Support hashing and de-/encryption using Vault's transit API.

src/main/java/de/stklcode/jvault/connector/model/response/TransitResponse.java

@@ -0,0 +1,92 @@
+/*
+ * Copyright 2016-2025 Stefan Kalscheuer
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package de.stklcode.jvault.connector.model.response;
+
+import java.util.Map;
+import java.util.Objects;
+
+import com.fasterxml.jackson.annotation.JsonSetter;
+
+/**
+ * Response entity for transit operations.
+ *
+ * @author Stefan Kalscheuer
+ * @since 1.5.0
+ */
+public class TransitResponse extends VaultDataResponse {
+
+    private static final long serialVersionUID = 6873804240772242771L;
+
+    private String ciphertext;
+    private String plaintext;
+    private String sum;
+
+    @JsonSetter("data")
+    private void setData(Map<String, String> data) {
+        ciphertext = data.get("ciphertext");
+        plaintext = data.get("plaintext");
+        sum = data.get("sum");
+    }
+
+    /**
+     * Get ciphertext.
+     * Populated after encryption.
+     *
+     * @return Ciphertext
+     */
+    public String getCiphertext() {
+        return ciphertext;
+    }
+
+    /**
+     * Get plaintext.
+     * Base64 encoded, populated after decryption.
+     *
+     * @return Plaintext
+     */
+    public String getPlaintext() {
+        return plaintext;
+    }
+
+    /**
+     * Get hash sum.
+     * Hex or Base64 string. Populated after hashing.
+     *
+     * @return Hash sum
+     */
+    public String getSum() {
+        return sum;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        } else if (o == null || getClass() != o.getClass() || !super.equals(o)) {
+            return false;
+        }
+        TransitResponse that = (TransitResponse) o;
+        return Objects.equals(ciphertext, that.ciphertext) &&
+            Objects.equals(plaintext, that.plaintext) &&
+            Objects.equals(sum, that.sum);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(super.hashCode(), ciphertext, plaintext, sum);
+    }
+}