init nostr and add userinfo provider

lib/data/metadata.dart

@@ -0,0 +1,70 @@
+class Metadata {
+  String? pubkey;
+  String? name;
+  String? displayName;
+  String? picture;
+  String? banner;
+  String? website;
+  String? about;
+  String? nip05;
+  String? lud16;
+  String? lud06;
+  int? updated_at;
+  int? valid;
+
+  Metadata({
+    this.pubkey,
+    this.name,
+    this.displayName,
+    this.picture,
+    this.banner,
+    this.website,
+    this.about,
+    this.nip05,
+    this.lud16,
+    this.lud06,
+    this.updated_at,
+    this.valid,
+  });
+
+  Metadata.fromJson(Map<String, dynamic> json) {
+    pubkey = json['pub_key'];
+    name = json['name'];
+    displayName = json['display_name'];
+    picture = json['picture'];
+    banner = json['banner'];
+    website = json['website'];
+    about = json['about'];
+    if (json['nip05'] != null && json['nip05'] is String) {
+      nip05 = json['nip05'];
+    }
+    lud16 = json['lud16'];
+    lud06 = json['lud06'];
+    if (json['updated_at'] != null && json['updated_at'] is int) {
+      updated_at = json['updated_at'];
+    }
+    valid = json['valid'];
+  }
+
+  Map<String, dynamic> toFullJson() {
+    var data = toJson();
+    data['pub_key'] = this.pubkey;
+    return data;
+  }
+
+  Map<String, dynamic> toJson() {
+    final Map<String, dynamic> data = new Map<String, dynamic>();
+    data['name'] = this.name;
+    data['display_name'] = this.displayName;
+    data['picture'] = this.picture;
+    data['banner'] = this.banner;
+    data['website'] = this.website;
+    data['about'] = this.about;
+    data['nip05'] = this.nip05;
+    data['lud16'] = this.lud16;
+    data['lud06'] = this.lud06;
+    data['updated_at'] = this.updated_at;
+    data['valid'] = this.valid;
+    return data;
+  }
+}