Save group message content types

[cameronvoell]

Part of #1403

Adds fields to group_messages table corresponding to ContentTypeId proto and saves them when sending and receiving messages.

ContentTypeId for reference:

https://github.com/xmtp/proto/blob/404a0f41a6dc00f5de5fcfc24856c8b4e417fe59/proto/mls/message_contents/content.proto#L10-L16

// ContentTypeId is used to identify the type of content stored in a Message.
message ContentTypeId {
  string authority_id = 1;  // authority governing this content type
  string type_id = 2;       // type identifier
  uint32 version_major = 3; // major version of the type
  uint32 version_minor = 4; // minor version of the type
}

[cameronvoell]

• Save group message content types #1435 : 2 dependent PRs (#1436 , #1440 ) 👈 (View in Graphite)
• main

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[insipx]

updated review