feat: multiple oauth providers (#355)

* feat: add flag decoder (candidate)

* refactor: finalize flags decoder

* feat: add env decoder

* feat: add oauth config parsing logic

* feat: implement backend logic for multiple oauth providers

* feat: implement multiple oauth providers in the frontend

* feat: add some default icons

* chore: add credits for parser

* feat: style oauth auto redirect screen

* fix: bot suggestions

* refactor: rework decoders using simpler and more efficient pattern

* refactor: rework oauth name database migration

internal/utils/decoders/flags_decoder.go

@@ -0,0 +1,30 @@
+package decoders
+
+import (
+	"strings"
+	"tinyauth/internal/config"
+
+	"github.com/traefik/paerser/parser"
+)
+
+func DecodeFlags(flags map[string]string) (config.Providers, error) {
+	filtered := filterFlags(flags)
+	normalized := NormalizeKeys(filtered, "tinyauth", "-")
+	var providers config.Providers
+
+	err := parser.Decode(normalized, &providers, "tinyauth", "tinyauth.providers")
+
+	if err != nil {
+		return config.Providers{}, err
+	}
+
+	return providers, nil
+}
+
+func filterFlags(flags map[string]string) map[string]string {
+	filtered := make(map[string]string)
+	for k, v := range flags {
+		filtered[strings.TrimPrefix(k, "--")] = v
+	}
+	return filtered
+}