Restructure code for more testaability

Move a number of funcs/files in the top-level `main` package into a new
`util` package, so test logic can directly invoke functions like
RunMark(), etc.  The main.go has been trimmed down to minimal sizing,
with former supporting funcs moved into `util` package, so they
can be run by unit tests.

Signed-off-by: Rich Scott <richscott@sent.com>

util/auth.go

@@ -0,0 +1,87 @@
+package util
+
+import (
+	"errors"
+	"io"
+	"net/url"
+	"os"
+	"strings"
+
+	"github.com/reconquest/karma-go"
+)
+
+type Credentials struct {
+	Username string
+	Password string
+	BaseURL  string
+	PageID   string
+}
+
+func GetCredentials(
+	username string,
+	password string,
+	targetURL string,
+	baseURL string,
+	compileOnly bool,
+
+) (*Credentials, error) {
+	var err error
+
+	if password == "" {
+		if !compileOnly {
+			return nil, errors.New(
+				"confluence password should be specified using -p " +
+					"flag or be stored in configuration file",
+			)
+		}
+		password = "none"
+	}
+
+	if password == "-" {
+		stdin, err := io.ReadAll(os.Stdin)
+		if err != nil {
+			return nil, karma.Format(
+				err,
+				"unable to read password from stdin",
+			)
+		}
+
+		password = string(stdin)
+	}
+
+	if compileOnly && targetURL == "" {
+		targetURL = "http://localhost"
+	}
+
+	url, err := url.Parse(targetURL)
+	if err != nil {
+		return nil, karma.Format(
+			err,
+			"unable to parse %q as url", targetURL,
+		)
+	}
+
+	if url.Host == "" {
+		if baseURL == "" {
+			return nil, errors.New(
+				"confluence base URL should be specified using -l " +
+					"flag or be stored in configuration file",
+			)
+		}
+	} else {
+		baseURL = url.Scheme + "://" + url.Host
+	}
+
+	baseURL = strings.TrimRight(baseURL, `/`)
+
+	pageID := url.Query().Get("pageId")
+
+	creds := &Credentials{
+		Username: username,
+		Password: password,
+		BaseURL:  baseURL,
+		PageID:   pageID,
+	}
+
+	return creds, nil
+}