feat(githubsync): add GitHub Sync plugin to sync epubs from a private GitHub repo on boot

plugins/githubsync/GitHubSync.h

@@ -0,0 +1,41 @@
+#pragma once
+
+#include <Arduino.h>
+#include <functional>
+#include <string>
+
+struct GitHubSyncConfig {
+    std::string username;
+    std::string pat;
+    std::string repo;
+    std::string branch;
+};
+
+enum class GitHubSyncResult {
+    OK,
+    NOT_CONFIGURED,
+    NO_WIFI,
+    AUTH_ERROR,
+    REPO_NOT_FOUND,
+    API_ERROR,
+    SD_ERROR,
+    PARSE_ERROR
+};
+
+using GitHubSyncProgressCallback = std::function<void(const std::string &status)>;
+
+class GitHubSync {
+public:
+    static bool loadConfig(GitHubSyncConfig &cfg);
+    static void saveConfig(const GitHubSyncConfig &cfg);
+    static bool isConfigured();
+    static GitHubSyncResult sync(GitHubSyncProgressCallback onProgress = nullptr);
+    static const char* resultMessage(GitHubSyncResult r);
+
+private:
+    static bool fetchFileList(const GitHubSyncConfig &cfg, std::string &outJson, GitHubSyncResult &err);
+    static bool downloadFile(const GitHubSyncConfig &cfg, const std::string &downloadUrl, const std::string &name, const std::string &sha, GitHubSyncResult &err, GitHubSyncProgressCallback onProgress);
+    static std::string loadLocalSha(const std::string &filename);
+    static void saveLocalSha(const std::string &filename, const std::string &sha);
+    static std::string shaFilePath(const std::string &filename);
+};