Refactor Package structure

This commit cleans up the package structure, to make two new top-level
packages `internal` (for internal-use packages) and `pkg` (for general
shared utility code).

pkg/password/password.go

@@ -0,0 +1,46 @@
+// Package password allows generating random passwords
+package password
+
+import (
+	"crypto/rand"
+	"math/big"
+	"strings"
+)
+
+// NOTE(twiesing): A bunch of scripts cannot properly handle the extra characters in the password.
+// For now it is disabled, but it should be re-enabled later.
+const PasswordCharSet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789" // + "!@#$%&*"
+var passwordCharCount = big.NewInt(int64(len(PasswordCharSet)))
+
+// Password returns a randomly generated string with the provided length.
+// It consists of alphanumeric characters only.
+//
+// When an error occurs, it is guaranteed to return "", err.
+// [rand.Reader] is used as the source of randomness.
+func Password(length int) (string, error) {
+	if length < 0 {
+		panic("length < 0")
+	}
+
+	// create a buffer to write the string to!
+	var password strings.Builder
+	password.Grow(length)
+
+	for i := 0; i < length; i++ {
+
+		// grab a random bIndex!
+		bIndex, err := rand.Int(rand.Reader, passwordCharCount)
+		if err != nil {
+			return "", err
+		}
+
+		// and use that index!
+		index := int(bIndex.Int64())
+		if err := password.WriteByte(PasswordCharSet[index]); err != nil {
+			return "", err
+		}
+	}
+
+	// return the password!
+	return password.String(), nil
+}