fix(sources/looker): Allow Looker to be configured without setting a Client Id or Secret (#1496)

Fixed a minor oversight from previous work on oauth.

docs/en/samples/looker/looker_gemini_oauth/_index.md

@@ -64,6 +64,7 @@ In this section, we will download Toolbox and run the Toolbox server.
    ```bash
     export LOOKER_BASE_URL=https://looker.example.com
     export LOOKER_VERIFY_SSL=true
+    export LOOKER_USE_CLIENT_OAUTH=true
    ```
 
    In some instances you may need to append `:19999` to

internal/sources/looker/looker.go

@@ -58,8 +58,8 @@ type Config struct {
 	Name               string `yaml:"name" validate:"required"`
 	Kind               string `yaml:"kind" validate:"required"`
 	BaseURL            string `yaml:"base_url" validate:"required"`
-	ClientId           string `yaml:"client_id" validate:"required"`
-	ClientSecret       string `yaml:"client_secret" validate:"required"`
+	ClientId           string `yaml:"client_id"`
+	ClientSecret       string `yaml:"client_secret"`
 	SslVerification    bool   `yaml:"verify_ssl"`
 	UseClientOAuth     bool   `yaml:"use_client_oauth"`
 	Timeout            string `yaml:"timeout"`

internal/sources/looker/looker_test.go

@@ -100,10 +100,8 @@ func TestFailParseFromYamlLooker(t *testing.T) {
 			sources:
 				my-looker-instance:
 					kind: looker
-					base_url: http://example.looker.com/
-					client_id: jasdl;k;tjl
 			`,
-			err: "unable to parse source \"my-looker-instance\" as \"looker\": Key: 'Config.ClientSecret' Error:Field validation for 'ClientSecret' failed on the 'required' tag",
+			err: "unable to parse source \"my-looker-instance\" as \"looker\": Key: 'Config.BaseURL' Error:Field validation for 'BaseURL' failed on the 'required' tag",
 		},
 	}
 	for _, tc := range tcs {