Implement v4 endpoints for OAuth (#6040)

* Implement POST /oauth/apps endpoint for APIv4

* Implement GET /oauth/apps endpoint for APIv4

* Implement GET /oauth/apps/{app_id} and /oauth/apps/{app_id}/info endpoints for APIv4

* Refactor API version independent oauth endpoints

* Implement DELETE /oauth/apps/{app_id} endpoint for APIv4

* Implement /oauth/apps/{app_id}/regen_secret endpoint for APIv4

* Implement GET /user/{user_id}/oauth/apps/authorized endpoint for APIv4

* Implement POST /oauth/deauthorize endpoint

model/authorize.go

@@ -6,6 +6,7 @@ package model
 import (
 	"encoding/json"
 	"io"
+	"net/http"
 )
 
 const (
@@ -25,6 +26,14 @@ type AuthData struct {
 	Scope       string `json:"scope"`
 }
 
+type AuthorizeRequest struct {
+	ResponseType string `json:"response_type"`
+	ClientId     string `json:"client_id"`
+	RedirectUri  string `json:"redirect_uri"`
+	Scope        string `json:"scope"`
+	State        string `json:"state"`
+}
+
 // IsValid validates the AuthData and returns an error if it isn't configured
 // correctly.
 func (ad *AuthData) IsValid() *AppError {
@@ -64,6 +73,33 @@ func (ad *AuthData) IsValid() *AppError {
 	return nil
 }
 
+// IsValid validates the AuthorizeRequest and returns an error if it isn't configured
+// correctly.
+func (ar *AuthorizeRequest) IsValid() *AppError {
+
+	if len(ar.ClientId) != 26 {
+		return NewAppError("AuthData.IsValid", "model.authorize.is_valid.client_id.app_error", nil, "", http.StatusBadRequest)
+	}
+
+	if len(ar.ResponseType) == 0 {
+		return NewAppError("AuthData.IsValid", "model.authorize.is_valid.response_type.app_error", nil, "", http.StatusBadRequest)
+	}
+
+	if len(ar.RedirectUri) == 0 || len(ar.RedirectUri) > 256 || !IsValidHttpUrl(ar.RedirectUri) {
+		return NewAppError("AuthData.IsValid", "model.authorize.is_valid.redirect_uri.app_error", nil, "client_id="+ar.ClientId, http.StatusBadRequest)
+	}
+
+	if len(ar.State) > 128 {
+		return NewAppError("AuthData.IsValid", "model.authorize.is_valid.state.app_error", nil, "client_id="+ar.ClientId, http.StatusBadRequest)
+	}
+
+	if len(ar.Scope) > 128 {
+		return NewAppError("AuthData.IsValid", "model.authorize.is_valid.scope.app_error", nil, "client_id="+ar.ClientId, http.StatusBadRequest)
+	}
+
+	return nil
+}
+
 func (ad *AuthData) PreSave() {
 	if ad.ExpiresIn == 0 {
 		ad.ExpiresIn = AUTHCODE_EXPIRE_TIME
@@ -98,6 +134,26 @@ func AuthDataFromJson(data io.Reader) *AuthData {
 	}
 }
 
+func (ar *AuthorizeRequest) ToJson() string {
+	b, err := json.Marshal(ar)
+	if err != nil {
+		return ""
+	} else {
+		return string(b)
+	}
+}
+
+func AuthorizeRequestFromJson(data io.Reader) *AuthorizeRequest {
+	decoder := json.NewDecoder(data)
+	var ar AuthorizeRequest
+	err := decoder.Decode(&ar)
+	if err == nil {
+		return &ar
+	} else {
+		return nil
+	}
+}
+
 func (ad *AuthData) IsExpired() bool {
 
 	if GetMillis() > ad.CreateAt+int64(ad.ExpiresIn*1000) {