Clean host URL in the auth login command (#1879)

## Changes
The host URL for databricks workspaces includes the workspaceId by
default as a positional arg. Eg:
https://e2-dogfood.staging.cloud.databricks.com/?o=1234

Thus a user can't simply copy paste the URL today to the auth login
command. They'll see a runtime error:
```
➜  cli git:(main) ✗ databricks auth login --host https://e2-dogfood.staging.cloud.databricks.com/\?o\=xxx --profile new-dg
Error: oidc: fetch .well-known: failed to unmarshal response body: invalid character '<' looking for beginning of value. This is likely a bug in the Databricks SDK for Go or the underlying REST API. Please report this issue with the following debugging information to the SDK issue tracker at https://github.com/databricks/databricks-sdk-go/issues. Request log:
GET /login.html
...
```

## Tests
Unit tests and manually. Now auth login works even when the workspace_id
is included in the URL.

libs/auth/oauth.go

@@ -9,6 +9,7 @@ import (
 	"errors"
 	"fmt"
 	"net"
+	"net/url"
 	"strings"
 	"time"
 
@@ -143,6 +144,26 @@ func (a *PersistentAuth) Challenge(ctx context.Context) error {
 	return nil
 }
 
+// This function cleans up the host URL by only retaining the scheme and the host.
+// This function thus removes any path, query arguments, or fragments from the URL.
+func (a *PersistentAuth) cleanHost() {
+	parsedHost, err := url.Parse(a.Host)
+	if err != nil {
+		return
+	}
+	// when either host or scheme is empty, we don't want to clean it. This is because
+	// the Go url library parses a raw "abc" string as the path of a URL and cleaning
+	// it will return thus return an empty string.
+	if parsedHost.Host == "" || parsedHost.Scheme == "" {
+		return
+	}
+	host := url.URL{
+		Scheme: parsedHost.Scheme,
+		Host:   parsedHost.Host,
+	}
+	a.Host = host.String()
+}
+
 func (a *PersistentAuth) init(ctx context.Context) error {
 	if a.Host == "" && a.AccountID == "" {
 		return ErrFetchCredentials
@@ -156,6 +177,9 @@ func (a *PersistentAuth) init(ctx context.Context) error {
 	if a.browser == nil {
 		a.browser = browser.OpenURL
 	}
+
+	a.cleanHost()
+
 	// try acquire listener, which we also use as a machine-local
 	// exclusive lock to prevent token cache corruption in the scope
 	// of developer machine, where this command runs.

libs/auth/oauth_test.go

@@ -228,3 +228,37 @@ func TestChallengeFailed(t *testing.T) {
 		assert.EqualError(t, err, "authorize: access_denied: Policy evaluation failed for this request")
 	})
 }
+
+func TestPersistentAuthCleanHost(t *testing.T) {
+	for _, tcases := range []struct {
+		in  string
+		out string
+	}{
+		{"https://example.com", "https://example.com"},
+		{"https://example.com/", "https://example.com"},
+		{"https://example.com/path", "https://example.com"},
+		{"https://example.com/path/subpath", "https://example.com"},
+		{"https://example.com/path?query=1", "https://example.com"},
+		{"https://example.com/path?query=1&other=2", "https://example.com"},
+		{"https://example.com/path#fragment", "https://example.com"},
+		{"https://example.com/path?query=1#fragment", "https://example.com"},
+		{"https://example.com/path?query=1&other=2#fragment", "https://example.com"},
+		{"https://example.com/path/subpath?query=1", "https://example.com"},
+		{"https://example.com/path/subpath?query=1&other=2", "https://example.com"},
+		{"https://example.com/path/subpath#fragment", "https://example.com"},
+		{"https://example.com/path/subpath?query=1#fragment", "https://example.com"},
+		{"https://example.com/path/subpath?query=1&other=2#fragment", "https://example.com"},
+		{"https://example.com/path?query=1%20value&other=2%20value", "https://example.com"},
+		{"http://example.com/path/subpath?query=1%20value&other=2%20value", "http://example.com"},
+
+		// URLs without scheme should be left as is
+		{"abc", "abc"},
+		{"abc.com/def", "abc.com/def"},
+	} {
+		p := &PersistentAuth{
+			Host: tcases.in,
+		}
+		p.cleanHost()
+		assert.Equal(t, tcases.out, p.Host)
+	}
+}