feat(bot): add Redis cache

proto/discord_cache.proto

@@ -0,0 +1,47 @@
+syntax = "proto3";
+
+package myriad.cache;
+
+message Overwrite {
+    uint64 id = 1;
+    int32 type = 2;
+    uint64 allow = 3;
+    uint64 deny = 4;
+}
+
+message CachedChannel {
+    uint64 id = 1;
+    int32 type = 2;
+    int32 position = 3;
+    string name = 4;
+    repeated Overwrite permission_overwrites = 5;
+    optional uint64 guild_id = 6;
+    optional uint64 parent_id = 7;
+}
+
+message CachedGuildMember {
+    repeated uint64 roles = 1;
+}
+
+message CachedGuild {
+    uint64 id = 1;
+    string name = 2;
+    uint64 owner_id = 3;
+    int32 premium_tier = 4;
+}
+
+message CachedRole {
+    uint64 id = 1;
+    string name = 2;
+    int32 position = 3;
+    uint64 permissions = 4;
+    bool mentionable = 5;
+}
+
+message CachedUser {
+    uint64 id = 1;
+    string username = 2;
+    string discriminator = 3;
+    optional string avatar = 4;
+    bool bot = 5;
+}