[api-minor] Implement securityHandler in the scripting API (bug 1731578)

src/core/crypto.js

@@ -1689,6 +1689,7 @@ const CipherTransformFactory = (function CipherTransformFactoryClosure() {
       if (!isName(filter, "Standard")) {
         throw new FormatError("unknown encryption method");
       }
+      this.filterName = filter.name;
       this.dict = dict;
       const algorithm = dict.get("V");
       if (

src/core/document.js

@@ -1161,6 +1161,9 @@ class PDFDocument {
     const docInfo = {
       PDFFormatVersion: version,
       Language: this.catalog.lang,
+      EncryptFilterName: this.xref.encrypt
+        ? this.xref.encrypt.filterName
+        : null,
       IsLinearized: !!this.linearization,
       IsAcroFormPresent: this.formInfo.hasAcroForm,
       IsXFAPresent: this.formInfo.hasXfa,