feat: Store fullchain certificate information alongside certs

src/main/java/de/mlessmann/certassist/openssl/CertificateUsage.java

@@ -1,6 +1,7 @@
 package de.mlessmann.certassist.openssl;
 
 import java.nio.file.Path;
+import org.springframework.lang.Nullable;
 
 /**
  * Instance of a certificate that is temporarily stored on disk to be available for use in command line calls.
@@ -8,8 +9,30 @@ import java.nio.file.Path;
  * @implSpec The files should be removed from disk when the instance is closed, UNLESS the provided paths are the permanent storage location for the certificate files.
  */
 public interface CertificateUsage extends AutoCloseable {
+    /**
+     * Returns the path to the certificate file (on disk, potentially temporary depending on the storage implementation).
+     */
     Path certificatePath();
+
+    /**
+     * Returns the path to the private key file (on disk, potentially temporary depending on the storage implementation).
+     * This file should also be encrypted.
+     * @see CertificatePasswordProvider
+     */
     Path certificateKeyPath();
+
+    /**
+     * Returns the path to the fullchain file (on disk, potentially temporary depending on the storage implementation).
+     * This should contain the entire certification chain from (inclusive) the certificate to the root authority (inclusive).
+     * @implSpec This method may return {@code null} if the certificate is self-signed.
+     */
+    @Nullable
+    Path fullchainPath();
+
+    /**
+     * String representation of the certificate's fingerprint.
+     * In case of OpenSSL, this should be in the form of: {@code SHA1;<HEX>:<HEX>:...}
+     */
     String fingerprint();
 
     @Override