Multiple playgrounds support (#215)

* Add Playground struct and basic support for creating it and retrieving
it

* Add missing functions in pwd mock

* Get playground from request domain and validate it exists. If valid set
it on the newly created session.

* Move playground specific configurations to the playground struct and use
it everytime we need that conf.

* Don't allow to specify a duration bigger that the allowed in the
playground

pwd/types/playground.go

@@ -0,0 +1,83 @@
+package types
+
+import (
+	"strconv"
+	"time"
+)
+
+type PlaygroundExtras map[string]interface{}
+
+func (e PlaygroundExtras) Get(name string) (interface{}, bool) {
+	v, f := e[name]
+	return v, f
+}
+func (e PlaygroundExtras) GetInt(name string) (int, bool) {
+	v, f := e[name]
+	if f {
+		if r, ok := v.(int); ok {
+			return r, ok
+		} else if r, ok := v.(float64); ok {
+			return int(r), ok
+		} else if r, ok := v.(string); ok {
+			if v, err := strconv.Atoi(r); err != nil {
+				return 0, false
+			} else {
+				return v, true
+			}
+		}
+		return v.(int), f
+	} else {
+		return 0, f
+	}
+}
+
+func (e PlaygroundExtras) GetString(name string) (string, bool) {
+	v, f := e[name]
+	if f {
+		if r, ok := v.(int); ok {
+			return strconv.Itoa(r), ok
+		} else if r, ok := v.(float64); ok {
+			return strconv.FormatFloat(r, 'g', -1, 64), ok
+		} else if r, ok := v.(bool); ok {
+			return strconv.FormatBool(r), ok
+		} else if r, ok := v.(string); ok {
+			return r, ok
+		} else {
+			return "", false
+		}
+	} else {
+		return "", f
+	}
+}
+
+func (e PlaygroundExtras) GetDuration(name string) (time.Duration, bool) {
+	v, f := e[name]
+	if f {
+		if r, ok := v.(int); ok {
+			return time.Duration(r), ok
+		} else if r, ok := v.(float64); ok {
+			return time.Duration(r), ok
+		} else if r, ok := v.(string); ok {
+			if d, err := time.ParseDuration(r); err != nil {
+				return time.Duration(0), false
+			} else {
+				return d, true
+			}
+		} else {
+			return time.Duration(0), false
+		}
+	} else {
+		return time.Duration(0), f
+	}
+}
+
+type Playground struct {
+	Id                          string           `json:"id" bson:"id"`
+	Domain                      string           `json:"domain" bson:"domain"`
+	DefaultDinDInstanceImage    string           `json:"default_dind_instance_image" bson:"default_dind_instance_image"`
+	AvailableDinDInstanceImages []string         `json:"available_dind_instance_images" bson:"available_dind_instance_images"`
+	AllowWindowsInstances       bool             `json:"allow_windows_instances" bson:"allow_windows_instances"`
+	DefaultSessionDuration      time.Duration    `json:"default_session_duration" bson:"default_session_duration"`
+	L2RouterIP                  string           `json:"l2_router_ip" bson:"l2_router_ip"`
+	Extras                      PlaygroundExtras `json:"extras" bson:"extras"`
+}