fix(blogpost): update author metadata (#251)

* fix(front-matter)

* updated front-matter for datasafe-uni-muenster post

* fix author metadata

Author: mfenner

src/blog-posts/2019-03-11-invenio-v310-released.md

@@ -1,6 +1,6 @@
 ---
 title: "Invenio v3.1.0 released"
-author: 
+authors: 
   - lnielsen
 date: 2019-03-11
 doi: https://doi.org/10.63517/cx376-czz04

src/blog-posts/2019-07-15-security-advisor-20190715.md

@@ -1,6 +1,6 @@
 ---
 title: "Invenio security releases - XSS and Host header injection"
-author: 
+authors: 
   - lnielsen
 date: 2019-07-15
 doi: https://doi.org/10.63517/afep7-29828

src/blog-posts/2019-12-20-invenio-v32-released.md

@@ -1,6 +1,6 @@
 ---
 title: "Invenio v3.2 released"
-author: 
+authors: 
   - lnielsen
 date: 2019-12-20
 doi: https://doi.org/10.63517/pt6rt-6mz56

src/blog-posts/2025-12-04-invenioils-product.md

@@ -1,8 +1,9 @@
 ---
 title: "Repositories and libraries: Invenio features InvenioILS!"
 authors: 
-  - Karolina Przerwa
+  - kpsherva
 date: 2026-01-01
+doi: https://doi.org/10.63517/hwttq-f5r06
 tags: 
   - InvenioILS
   - Showcase