disco: Support OAuth scopes in OAuth client discovery

Support for scopes is required for OAuth2 server
implementations that are following the additional
requirements imposed by the OpenID Connect
specification.

disco/host.go

@@ -255,6 +255,17 @@ func (h *Host) ServiceOAuthClient(id string) (*OAuthClient, error) {
 		ret.MinPort = 1024
 		ret.MaxPort = 65535
 	}
+	if scopesRaw, ok := raw["scopes"].([]interface{}); ok {
+		var scopes []string
+		for _, scopeI := range scopesRaw {
+			scope, ok := scopeI.(string)
+			if !ok {
+				return nil, fmt.Errorf("Invalid \"scopes\" for service %s: all scopes must be strings", id)
+			}
+			scopes = append(scopes, scope)
+		}
+		ret.Scopes = scopes
+	}
 
 	return ret, nil
 }

disco/host_test.go

@@ -148,6 +148,24 @@ func TestHostServiceOAuthClient(t *testing.T) {
 				"authz":  "/foo",
 				"token":  "***not A URL at all!:/<@@@@>***",
 			},
+			"scopesincluded.v1": map[string]interface{}{
+				"client": "scopesincluded",
+				"authz":  "/auth",
+				"token":  "/token",
+				"scopes": []interface{}{"app1.full_access", "app2.read_only"},
+			},
+			"scopesempty.v1": map[string]interface{}{
+				"client": "scopesempty",
+				"authz":  "/auth",
+				"token":  "/token",
+				"scopes": []interface{}{},
+			},
+			"scopesbad.v1": map[string]interface{}{
+				"client": "scopesbad",
+				"authz":  "/auth",
+				"token":  "/token",
+				"scopes": []interface{}{"app1.full_access", 42},
+			},
 		},
 	}
 
@@ -290,6 +308,36 @@ func TestHostServiceOAuthClient(t *testing.T) {
 			nil,
 			"Failed to parse token URL: parse \"***not A URL at all!:/<@@@@>***\": first path segment in URL cannot contain colon",
 		},
+		{
+			"scopesincluded.v1",
+			&OAuthClient{
+				ID:                  "scopesincluded",
+				AuthorizationURL:    mustURL(t, "https://example.com/auth"),
+				TokenURL:            mustURL(t, "https://example.com/token"),
+				MinPort:             1024,
+				MaxPort:             65535,
+				SupportedGrantTypes: NewOAuthGrantTypeSet("authz_code"),
+				Scopes:              []string{"app1.full_access", "app2.read_only"},
+			},
+			"",
+		},
+		{
+			"scopesempty.v1",
+			&OAuthClient{
+				ID:                  "scopesempty",
+				AuthorizationURL:    mustURL(t, "https://example.com/auth"),
+				TokenURL:            mustURL(t, "https://example.com/token"),
+				MinPort:             1024,
+				MaxPort:             65535,
+				SupportedGrantTypes: NewOAuthGrantTypeSet("authz_code"),
+			},
+			"",
+		},
+		{
+			"scopesbad.v1",
+			nil,
+			`Invalid "scopes" for service scopesbad.v1: all scopes must be strings`,
+		},
 	}
 
 	for _, test := range tests {

disco/oauth_client.go

@@ -46,6 +46,11 @@ type OAuthClient struct {
 	// by the server, even if a particular keyword is not supported by the
 	// current version of Terraform.
 	SupportedGrantTypes OAuthGrantTypeSet
+
+	// Oauth2 does not require scopes for the authorization endpoint, however
+	// OIDC does. Optional list of scopes to include in auth code and token
+	// requests.
+	Scopes []string
 }
 
 // Endpoint returns an oauth2.Endpoint value ready to be used with the oauth2