Revert "Remove unused test data files"

This reverts commit ef24980e667debd0cb8f1f26218c452bacbbe084.
diff --git a/tests/data_files/server1.crt.openssl.v3_ext b/tests/data_files/server1.crt.openssl.v3_ext
new file mode 100644
index 0000000..239d56a
--- /dev/null
+++ b/tests/data_files/server1.crt.openssl.v3_ext
@@ -0,0 +1,4 @@
+[v3_ext]
+basicConstraints = CA:false
+subjectKeyIdentifier=hash
+authorityKeyIdentifier=keyid