Start abstracting away the ACME provider (#830)

* Start abstracting away the ACME provider

* Move ACME to interface with sub-package implementations

* Addressing comments

* Library -> Provider

* Missed a couple of Library -> Provider

* One more Library -> Provider

* remove constants

api/server/options.go

@@ -2,15 +2,24 @@ package server
 
 import (
 	"crypto/tls"
+
+	"github.com/micro/go-micro/api/server/acme"
 )
 
 type Option func(o *Options)
 
 type Options struct {
-	EnableACME bool
-	EnableTLS  bool
-	ACMEHosts  []string
-	TLSConfig  *tls.Config
+	EnableACME   bool
+	ACMEProvider acme.Provider
+	EnableTLS    bool
+	ACMEHosts    []string
+	TLSConfig    *tls.Config
+}
+
+func EnableACME(b bool) Option {
+	return func(o *Options) {
+		o.EnableACME = b
+	}
 }
 
 func ACMEHosts(hosts ...string) Option {
@@ -19,9 +28,9 @@ func ACMEHosts(hosts ...string) Option {
 	}
 }
 
-func EnableACME(b bool) Option {
+func ACMEProvider(p acme.Provider) Option {
 	return func(o *Options) {
-		o.EnableACME = b
+		o.ACMEProvider = p
 	}
 }