fix: remove magic string duplication on aip detail form

src/app/features/preservation/aip/components/presentationals/aip-form/aip-form.presentational.ts

@@ -79,14 +79,18 @@ export class AipFormPresentational extends SharedAbstractFormPresentational<AipE
     let lastChecksumCheckSuccess = StringUtil.stringEmpty;
     let lastChecksumCheckFail = StringUtil.stringEmpty;
 
+    const keyLabelNever = "aip.form.lastChecksumCheck.never";
+    const keyLabelSuccess = "aip.form.lastChecksumCheck.success";
+    const keyLabelFail = "aip.form.lastChecksumCheck.fail";
+
     this.translate.get([
-      "aip.form.lastChecksumCheck.never",
-      "aip.form.lastChecksumCheck.success",
-      "aip.form.lastChecksumCheck.fail"
+      keyLabelNever,
+      keyLabelSuccess,
+      keyLabelFail
     ]).subscribe(translation => {
-      lastChecksumCheckNever = translation["aip.form.lastChecksumCheck.never"];
-      lastChecksumCheckSuccess = translation["aip.form.lastChecksumCheck.success"];
-      lastChecksumCheckFail = translation["aip.form.lastChecksumCheck.fail"];
+      lastChecksumCheckNever = translation[keyLabelNever];
+      lastChecksumCheckSuccess = translation[keyLabelSuccess];
+      lastChecksumCheckFail = translation[keyLabelFail];
     });
 
     if (isNullOrUndefined(checksum)) {