Add initial support for CentOS 9

This is an attempt to introduce initial support for CentOS 9, and fixes
the missing gpg key file for CentOS 9.

files/RPM-GPG-KEY-EPEL-9

@@ -0,0 +1,29 @@
+-----BEGIN PGP PUBLIC KEY BLOCK-----
+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+=Mjs/
+-----END PGP PUBLIC KEY BLOCK-----

metadata.json

@@ -12,14 +12,16 @@
       "operatingsystem": "RedHat",
       "operatingsystemrelease": [
         "7",
-        "8"
+        "8",
+        "9"
       ]
     },
     {
       "operatingsystem": "CentOS",
       "operatingsystemrelease": [
         "7",
-        "8"
+        "8",
+        "9"
       ]
     },
     {