Friends functionality (#90)

### Description

Implements and closes #86

### Game

Robocraft

### Please confirm

- [x] I am the legal owner or represent the owner of all work submitted
- [x] I consent to my submission being added to this FOSS project
- [ ] This PR used LLMs to generate some or all of the code changes

Reviewed-on: https://git.ngram.ca/OpenJam/rc-servers/pulls/90
Co-authored-by: NG (Graham) <ngniusness@gmail.com>
Co-committed-by: NG (Graham) <ngniusness@gmail.com>

rc_social_room/src/data/friend.rs

@@ -16,4 +16,90 @@ impl AvatarInfo {
     }
 }
 
-// TODO pub struct FriendInfo {}
+#[derive(Debug, Clone)]
+pub struct FriendInfo {
+    pub status: InviteStatus,
+    pub is_online: bool,
+    pub public_id: String,
+    pub display_name: String,
+    pub clan_name: String,
+}
+
+impl FriendInfo {
+    pub(super) fn dump(&self, w: &mut dyn std::io::Write) -> std::io::Result<usize> {
+        w.write_all(&[
+            self.status.as_u8(),
+            self.is_online as u8,
+        ])?;
+        let mut total = 2;
+        total += oj_rc_core::data::write_str_for_binreader(&self.public_id, w)?;
+        total += oj_rc_core::data::write_str_for_binreader(&self.display_name, w)?;
+        total += oj_rc_core::data::write_str_for_binreader(&self.clan_name, w)?;
+        Ok(total)
+    }
+
+    pub(super) fn parse(r: &mut dyn std::io::Read) -> std::io::Result<Self> {
+        let mut buf = [0u8; 2];
+        r.read_exact(&mut buf)?;
+        let status = InviteStatus::from_u8(buf[0]).ok_or_else(|| std::io::Error::other(format!("Invalid invite status {}", buf[0])))?;
+        let is_online = buf[1] != 0;
+        let public_id = oj_rc_core::data::read_str_for_binwriter(r)?;
+        let display_name = oj_rc_core::data::read_str_for_binwriter(r)?;
+        let clan_name = oj_rc_core::data::read_str_for_binwriter(r)?;
+        Ok(Self {
+            status,
+            is_online,
+            public_id,
+            display_name,
+            clan_name,
+        })
+    }
+}
+
+#[repr(u8)]
+#[derive(Debug, Clone, Copy)]
+pub enum InviteStatus {
+    InviteSent = 0,
+    InvitePending = 1,
+    Accepted = 2,
+    None = 3
+}
+
+impl InviteStatus {
+    #[inline]
+    pub fn from_u8(num: u8) -> Option<Self> {
+        match num {
+            0 => Some(Self::InviteSent),
+            1 => Some(Self::InvitePending),
+            2 => Some(Self::Accepted),
+            3 => Some(Self::None),
+            _ => None,
+        }
+    }
+
+    #[inline]
+    pub fn as_u8(&self) -> u8 {
+        *self as u8
+    }
+
+    pub fn from_core(core: &oj_rc_core::persist::user::FriendInviteStatus) -> Self {
+        match core {
+            oj_rc_core::persist::user::FriendInviteStatus::InviteSent => Self::InviteSent,
+            oj_rc_core::persist::user::FriendInviteStatus::InvitePending => Self::InvitePending,
+            oj_rc_core::persist::user::FriendInviteStatus::Accepted => Self::Accepted,
+            oj_rc_core::persist::user::FriendInviteStatus::Declined
+            | oj_rc_core::persist::user::FriendInviteStatus::Cancelled
+            | oj_rc_core::persist::user::FriendInviteStatus::Removed => Self::None,
+        }
+    }
+
+    #[inline]
+    pub fn reciprocal(&self) -> Self {
+        match self {
+            Self::InviteSent => Self::InvitePending,
+            Self::InvitePending => Self::InviteSent,
+            Self::Accepted => Self::Accepted,
+            Self::None => Self::None,
+        }
+    }
+}