Added minimal-responses plugin (#4417)

* Added minimal-responses plugin

Signed-off-by: Soumya Ghosh Dastidar <gdsoumya@gmail.com>

* Removed unnecessary comments

* Updated tests

Signed-off-by: Soumya Ghosh Dastidar <gdsoumya@gmail.com>

* Reformated imports

Signed-off-by: Soumya Ghosh Dastidar <gdsoumya@gmail.com>

* Updated package name

Signed-off-by: Soumya Ghosh Dastidar <gdsoumya@gmail.com>

* Removed  unnecessary comments

Co-authored-by: Miek Gieben <miek@miek.nl>

* Added changes

Signed-off-by: Soumya Ghosh Dastidar <gdsoumya@gmail.com>

* updated

Signed-off-by: Soumya Ghosh Dastidar <gdsoumya@gmail.com>

* Updated comment for NextOrFailure

Signed-off-by: Soumya Ghosh Dastidar <gdsoumya@gmail.com>

* Updated to test.Case for testing

Signed-off-by: Soumya Ghosh Dastidar <gdsoumya@gmail.com>

* Formated imports using goimports

Signed-off-by: Soumya Ghosh Dastidar <gdsoumya@gmail.com>

Co-authored-by: Miek Gieben <miek@miek.nl>

plugin/minimal/README.md

@@ -0,0 +1,36 @@
+# minimal
+
+## Name
+
+*minimal* - minimizes size of the DNS response message whenever possible.
+
+## Description
+
+The *minimal* plugin tries to minimize the size of the response. Depending on the response type it 
+removes resource records from the AUTHORITY and ADDITIONAL sections.
+
+Specifically this plugin looks at successful responses (this excludes negative responses, i.e.
+nodata or name error). If the successful response isn't a delegation only the RRs in the answer
+section are written to the client.
+
+## Syntax
+
+~~~ txt
+minimal
+~~~
+
+## Examples
+
+Enable minimal responses:
+
+~~~ corefile
+example.org {
+    whoami
+    forward . 8.8.8.8
+    minimal
+}
+~~~
+
+## See Also
+
+[BIND 9 Configuration Reference](https://bind9.readthedocs.io/en/latest/reference.html#boolean-options)