Remove the word middleware (#1067)

* Rename middleware to plugin

first pass; mostly used 'sed', few spots where I manually changed
text.

This still builds a coredns binary.

* fmt error

* Rename AddMiddleware to AddPlugin

* Readd AddMiddleware to remain backwards compat

1 files changed, 52 insertions, 0 deletions

diff --git a/plugin/tls/README.md b/plugin/tls/README.md
new file mode 100644
index 000000000..d2a56f793
--- /dev/null
+++ b/plugin/tls/README.md
@@ -0,0 +1,52 @@
+# tls
+
+*tls* allows you to configure the server certificates for the TLS and gRPC servers.
+For other types of servers it is ignored.
+
+CoreDNS supports queries that are encrypted using TLS (DNS over Transport Layer Security, RFC 7858)
+or are using gRPC (https://grpc.io/, not an IETF standard). Normally DNS traffic isn't encrypted at
+all (DNSSEC only signs resource records).
+
+The *proxy* plugin also support gRPC (`protocol gRPC`), meaning you can chain CoreDNS servers
+using this protocol.
+
+The *tls* "plugin" allows you to configure the cryptographic keys that are needed for both
+DNS-over-TLS and DNS-over-gRPC. If the `tls` directive is omitted, then no encryption takes place.
+
+The gRPC protobuffer is defined in `pb/dns.proto`. It defines the proto as a simple wrapper for the
+wire data of a DNS message.
+
+## Syntax
+
+~~~ txt
+tls CERT KEY CA
+~~~
+
+## Examples
+
+Start a DNS-over-TLS server that picks up incoming DNS-over-TLS queries on port 5553 and uses the
+nameservers defined in `/etc/resolv.conf` to resolve the query. This proxy path uses plain old DNS.
+
+~~~
+tls://.:5553 {
+	tls cert.pem key.pem ca.pem
+	proxy . /etc/resolv.conf
+}
+~~~
+
+Start a DNS-over-gRPC server that is similar to the previous example, but using DNS-over-gRPC for
+incoming queries.
+
+~~~
+grpc://. {
+	tls cert.pem key.pem ca.pem
+	proxy . /etc/resolv.conf
+}
+~~~
+
+Only Knot DNS' `kdig` supports DNS-over-TLS queries, no command line client supports gRPC making
+debugging these transports harder than it should be.
+
+## Also See
+
+RFC 7858 and https://grpc.io.