Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

server/channels/utils/license-public-key.txt

@@ -0,0 +1,9 @@
+-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAyZmShlU8Z8HdG0IWSZ8r
+tSyzyxrXkJjsFUf0Ke7bm/TLtIggRdqOcUF3XEWqQk5RGD5vuq7Rlg1zZqMEBk8N
+EZeRhkxyaZW8pLjxwuBUOnXfJew31+gsTNdKZzRjrvPumKr3EtkleuoxNdoatu4E
+HrKmR/4Yi71EqAvkhk7ZjQFuF0osSWJMEEGGCSUYQnTEqUzcZSh1BhVpkIkeu8Kk
+1wCtptODixvEujgqVe+SrE3UlZjBmPjC/CL+3cYmufpSNgcEJm2mwsdaXp2OPpfn
+a0v85XL6i9ote2P+fLZ3wX9EoioHzgdgB7arOxY50QRJO7OyCqpKFKv6lRWTXuSt
+hwIDAQAB
+-----END PUBLIC KEY-----