feat(api): Add support for HTTP override (spark-jobserver#883)

Author: marcoboi

README.md

@@ -50,6 +50,7 @@ Also see [Chinese docs / 中文](doc/chinese/job-server.md).
   - [Context configuration](#context-configuration)
   - [Other configuration settings](#other-configuration-settings)
   - [Job Result Serialization](#job-result-serialization)
+  - [HTTP Override](#http-override)
 - [Clients](#clients)
 - [Contribution and Development](#contribution-and-development)
   - [Publishing packages](#publishing-packages)
@@ -791,6 +792,19 @@ serialized properly:
 
 If we encounter a data type that is not supported, then the entire result will be serialized to a string.
 
+### HTTP Override
+
+Spark Job Server offers HTTP override functionality. 
+Often reverse proxies and firewall implement access limitations to, for example, DELETE and PUT requests.
+HTTP override allows overcoming these limitations by wrapping, for example, a DELETE request into a POST request.
+
+Requesting the destruction of a context can be accomplished through HTTP override using the following syntax: 
+    
+    $ curl -X POST "localhost:8090/contexts/test_context?_method=DELETE"
+
+Here, a DELETE request is passed to Spark Job Server "through" a POST request.
+    
+    
 ## Clients
 
 Spark Jobserver project has a

job-server/src/main/scala/spark/jobserver/WebApi.scala

@@ -139,8 +139,10 @@ class WebApi(system: ActorSystem,
   val logger = LoggerFactory.getLogger(getClass)
 
   val myRoutes = cors {
-    binaryRoutes ~ jarRoutes ~ contextRoutes ~ jobRoutes ~
-      dataRoutes ~ healthzRoutes ~ otherRoutes
+    overrideMethodWithParameter("_method") {
+      binaryRoutes ~ jarRoutes ~ contextRoutes ~ jobRoutes ~
+        dataRoutes ~ healthzRoutes ~ otherRoutes
+    }
   }
 
   lazy val authenticator: AuthMagnet[AuthInfo] = {