feat: consistent flags and environment variables (#5549)

- In the root command, all flags are now correctly available as environmental variables, except for `--config` flag. This was already supposed to be the case, but due to bugs in the implementation it didn't work properly.
- All configuration options (unless I missed something) that are available as flags should now properly update the configuration when using the `config init` and `config set` commands.
- Flag names are now consistently in the lowerCamelCase format. All flags that were in a different format have been updated in a backwards compatible way. For a transitionary period of at least 6 months, both will work:
  - `--dir-mode` --> `--dirMode`
  - `--hide-login-button` --> `--hideLoginButton`
  - `--create-user-dir` --> `--createUserDir`
  - `--minimum-password-length` --> `--minimumPasswordLength`
  - `--socket-perm` --> `--socketPerm`
  - `--disable-thumbnails` --> `--disableThumbnails`
  - `--disable-preview-resize` --> `--disablePreviewResize`
  - `--disable-exec` --> `--disableExec`
  - `--disable-type-detection-by-header` --> `--disableTypeDetectionByHeader`
  - `--img-processors` --> `--imageProcessors`
  - `--cache-dir` --> `--cacheDir`
  - `--token-expiration-time` --> `--tokenExpirationTime`
  - `--baseurl` --> `--baseURL`

cmd/cmd_test.go

@@ -0,0 +1,35 @@
+package cmd
+
+import (
+	"testing"
+
+	"github.com/samber/lo"
+	"github.com/spf13/cobra"
+)
+
+// TestEnvCollisions ensures that there are no collisions in the produced environment
+// variable names for all commands and their flags.
+func TestEnvCollisions(t *testing.T) {
+	testEnvCollisions(t, rootCmd)
+}
+
+func testEnvCollisions(t *testing.T, cmd *cobra.Command) {
+	for _, cmd := range cmd.Commands() {
+		testEnvCollisions(t, cmd)
+	}
+
+	replacements := generateEnvKeyReplacements(cmd)
+	envVariables := []string{}
+
+	for i := range replacements {
+		if i%2 != 0 {
+			envVariables = append(envVariables, replacements[i])
+		}
+	}
+
+	duplicates := lo.FindDuplicates(envVariables)
+
+	if len(duplicates) > 0 {
+		t.Errorf("Found duplicate environment variable keys for command %q: %v", cmd.Name(), duplicates)
+	}
+}