Adding Communication CallingServer API preview 0. (Azure#14543)

* Adding Communication CallingServer API preview1.

* Updated the Swagger to add PlayAudio api for out-call scenario (Azure#14578)

* Updated the servercalling swagger with playAudio api for out-call
* Fixed a typo

Co-authored-by: Paresh Arvind Patil <papati@microsoft.com>

* Add preview0 swagger for .net sdk.

* Update SDK Swagger preview0

* Update swagger api version.

* Update swagger api version.

* Removed Model and Internal postfix, added events in swagger (Azure#14639)

* Removed Model and Internal postfix, added events in swagger

* update the title

* Add swagger for version 2021-06-15 (Azure#14720)

* Updated swagger with version 2021-06-15

* Fix the Communication.Common definitions path

* Removed old swagger

* Added unhold to list of custom-word

* Update readme file accourding to new swagger.

* update responses model suffix to result

* Removed error responses and consumes/produces values from all the apis. Changed invite participant to add participant. Other model name related changes.

* Added examples for all the apis.

* Removed error responses from example

* Added back error response type, added response body for add participant operation

* Fix join call example

* Update the examples

Co-authored-by: Paresh Arvind Patil <patilaparesh@gmail.com>
Co-authored-by: Paresh Arvind Patil <papati@microsoft.com>
Co-authored-by: navali-msft <66667092+navali-msft@users.noreply.github.com>
Co-authored-by: Naveed Ali <navali@microsoft.com>

custom-words.txt

@@ -1430,6 +1430,7 @@ provisioningservices
 provisioningState
 Psec
 PSNR
+pstn
 ptrdname
 publicipaddresses
 publicpreview
@@ -1808,6 +1809,7 @@ streamingendpoint
 streamingjobs
 streamingservice
 subcause
+subcode
 subcomponent
 subcomponents
 subdir
@@ -1970,6 +1972,7 @@ Undeleting
 unencrypted
 unexamined
 unhide
+unhold
 Unigrams
 uniqueidentifier
 uniquestring