Added documentation for GameServer API swagger (#397)

* added documentation for GameServer API swagger

* fixes the main.go path

docs/gameserverapi/gameserverapi_swagger.md

@@ -0,0 +1,37 @@
+---
+layout: default
+title: Swagger for GameServer API
+parent: GameServer API
+nav_order: 2
+---
+
+## Swagger for GameServer API
+
+The API uses [swag](https://github.com/swaggo/swag) and [gin-swagger](https://github.com/swaggo/gin-swagger) packages from Swaggo to generate Restful API documentation with Swagger 2.0.
+
+## How to use swag
+
+Swag parses the API annotations to generate Swagger 2.0 documentation. Whenever there is a change in API annotations, we need to re-generate swagger docs using below command -
+
+```bash
+swag init -g cmd/gameserverapi/main.go --parseDependency
+```
+
+> **_NOTE_**: _--parseDependency_ is used to generate model definitions that inherit or depends on other type definitions. If the dependency depth is too high, use the _--parseDepth_ flag and set it to the required depth.
+
+Swagger Host and BasePath are set automatically using gin context during CORSMiddleware injection. To change this behavior, please refer to the code below in [main.go](https://github.com/PlayFab/thundernetes/blob/main/cmd/gameserverapi/main.go)
+
+```go
+func setSwaggerInfo(c *gin.Context) {
+ // dynamically sets swagger host and base path
+ docs.SwaggerInfo.Host = c.Request.Host
+ docs.SwaggerInfo.BasePath = urlprefix
+}
+```
+
+## Browse Swagger
+
+Run the code and browse the following URL to use swagger -
+<https://{$IP}:5001/swagger/index.html> or in case of localhost - <http://localhost:5001/swagger/index.html>
+
+!["GameServer API Swagger"](../assets/images/gameserverapi_swagger.png "GameServer API Swagger")