GODRIVER-523: Support new readConcern level "available"

Author: igorKryvenko

core/readconcern/readconcern.go

@@ -40,6 +40,12 @@ func Linearizable() *ReadConcern {
 	return New(Level("linearizable"))
 }
 
+// Available specifies that the query should return data from the instance with no guarantee
+// that the data has been written to a majority of the replica set members (i.e. may be rolled back).
+func Available() *ReadConcern {
+	return New(Level("available"))
+}
+
 // New constructs a new read concern from the given string.
 func New(options ...Option) *ReadConcern {
 	concern := &ReadConcern{}

data/read-write-concern/connection-string/read-concern.json

@@ -24,6 +24,15 @@
       "readConcern": {
         "level": "majority"
       }
+    },
+    {
+      "description": "available specified",
+      "uri": "mongodb://localhost/?readConcernLevel=available",
+      "valid": true,
+      "warning": false,
+      "readConcern": {
+        "level": "available"
+      }
     }
   ]
 }

data/read-write-concern/connection-string/read-concern.yml

@@ -17,3 +17,9 @@ tests:
         valid: true
         warning: false
         readConcern: { level: "majority" }
+    -
+        description: "available specified"
+        uri: "mongodb://localhost?readConcernLevel=available"
+        valid: true
+        warning: false
+        readConcern: { level: "available" }

data/read-write-concern/document/read-concern.json

@@ -28,6 +28,17 @@
         "level": "local"
       },
       "isServerDefault": false
+    },
+    {
+      "description": "Available",
+      "valid": true,
+      "readConcern": {
+        "level": "available"
+      },
+      "readConcernDocument": {
+        "level": "available"
+      },
+      "isServerDefault": false
     }
   ]
 }

data/read-write-concern/document/read-concern.yml

@@ -16,4 +16,10 @@ tests:
         valid: true
         readConcern: { level: "local" }
         readConcernDocument: { level: "local" }
+        isServerDefault: false
+    -
+        description: "Available"
+        valid: true
+        readConcern: { level: "available" }
+        readConcernDocument: { level: "available" }
         isServerDefault: false