Refactor traefik with package

Split a bit traefik into package. The idea behind this refactor is to
start move inter-dependencies away and do some DRY or SRP.

- Adds a `provider` package, with providers except `web.go`
- Adds a `types` package with common struct.
- Move `gen.go` to an `autogen` package

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

types/types.go

@@ -0,0 +1,81 @@
+package types
+
+import (
+	"errors"
+	"strings"
+)
+
+// Backend configuration
+type Backend struct {
+	Servers        map[string]Server `json:"servers,omitempty"`
+	CircuitBreaker *CircuitBreaker   `json:"circuitBreaker,omitempty"`
+	LoadBalancer   *LoadBalancer     `json:"loadBalancer,omitempty"`
+}
+
+// LoadBalancer configuration
+type LoadBalancer struct {
+	Method string `json:"method,omitempty"`
+}
+
+// CircuitBreaker configuration
+type CircuitBreaker struct {
+	Expression string `json:"expression,omitempty"`
+}
+
+// Server configuration
+type Server struct {
+	URL    string `json:"url,omitempty"`
+	Weight int    `json:"weight,omitempty"`
+}
+
+// Route configuration
+type Route struct {
+	Rule  string `json:"rule,omitempty"`
+	Value string `json:"value,omitempty"`
+}
+
+// Frontend configuration
+type Frontend struct {
+	Backend        string           `json:"backend,omitempty"`
+	Routes         map[string]Route `json:"routes,omitempty"`
+	PassHostHeader bool             `json:"passHostHeader,omitempty"`
+}
+
+// Load Balancer Method
+type LoadBalancerMethod uint8
+
+const (
+	// Wrr (default) = Weighted Round Robin
+	Wrr LoadBalancerMethod = iota
+	// Drr = Dynamic Round Robin
+	Drr
+)
+
+var loadBalancerMethodNames = []string{
+	"Wrr",
+	"Drr",
+}
+
+func NewLoadBalancerMethod(loadBalancer *LoadBalancer) (LoadBalancerMethod, error) {
+	if loadBalancer != nil {
+		for i, name := range loadBalancerMethodNames {
+			if strings.EqualFold(name, loadBalancer.Method) {
+				return LoadBalancerMethod(i), nil
+			}
+		}
+	}
+	return Wrr, ErrInvalidLoadBalancerMethod
+}
+
+var ErrInvalidLoadBalancerMethod = errors.New("Invalid method, using default")
+
+// Configuration of a provider
+type Configuration struct {
+	Backends  map[string]*Backend  `json:"backends,omitempty"`
+	Frontends map[string]*Frontend `json:"frontends,omitempty"`
+}
+
+type ConfigMessage struct {
+	ProviderName  string
+	Configuration *Configuration
+}