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/app_utils.go

@@ -6,6 +6,9 @@ import (
 	"net/url"
 	"strings"
 	"tinyauth/internal/config"
+	"tinyauth/internal/utils/decoders"
+
+	"maps"
 
 	"github.com/gin-gonic/gin"
 	"github.com/rs/zerolog"
@@ -130,3 +133,68 @@ func GetLogLevel(level string) zerolog.Level {
 		return zerolog.InfoLevel
 	}
 }
+
+func GetOAuthProvidersConfig(env []string, args []string, appUrl string) (map[string]config.OAuthServiceConfig, error) {
+	providers := make(map[string]config.OAuthServiceConfig)
+
+	// Get from environment variables
+	envMap := make(map[string]string)
+
+	for _, e := range env {
+		pair := strings.SplitN(e, "=", 2)
+		if len(pair) == 2 {
+			envMap[pair[0]] = pair[1]
+		}
+	}
+
+	envProviders, err := decoders.DecodeEnv(envMap)
+
+	if err != nil {
+		return nil, err
+	}
+
+	maps.Copy(providers, envProviders.Providers)
+
+	// Get from flags
+	flagsMap := make(map[string]string)
+
+	for _, arg := range args[1:] {
+		if strings.HasPrefix(arg, "--") {
+			pair := strings.SplitN(arg[2:], "=", 2)
+			if len(pair) == 2 {
+				flagsMap[pair[0]] = pair[1]
+			}
+		}
+	}
+
+	flagProviders, err := decoders.DecodeFlags(flagsMap)
+
+	if err != nil {
+		return nil, err
+	}
+
+	maps.Copy(providers, flagProviders.Providers)
+
+	// For every provider get correct secret from file if set
+	for name, provider := range providers {
+		secret := GetSecret(provider.ClientSecret, provider.ClientSecretFile)
+		provider.ClientSecret = secret
+		provider.ClientSecretFile = ""
+		providers[name] = provider
+	}
+
+	// If we have google/github providers and no redirect URL babysit them
+	babysitProviders := []string{"google", "github"}
+
+	for _, name := range babysitProviders {
+		if provider, exists := providers[name]; exists {
+			if provider.RedirectURL == "" {
+				provider.RedirectURL = appUrl + "/api/oauth/callback/" + name
+				providers[name] = provider
+			}
+		}
+	}
+
+	// Return combined providers
+	return providers, nil
+}