get content id strings straight from codecs

xmtp_content_types/src/group_updated.rs

@@ -10,7 +10,7 @@ pub struct GroupUpdatedCodec {}
 
 impl GroupUpdatedCodec {
     const AUTHORITY_ID: &'static str = "xmtp.org";
-    const TYPE_ID: &'static str = "group_updated";
+    pub const TYPE_ID: &'static str = "group_updated";
 }
 
 impl ContentCodec<GroupUpdated> for GroupUpdatedCodec {

xmtp_content_types/src/lib.rs

@@ -30,19 +30,19 @@ pub enum ContentType {
 impl ContentType {
     pub fn from_string(type_id: &str) -> Self {
         match type_id {
-            "text" => Self::Text,
-            "group_membership_change" => Self::GroupMembershipChange,
-            "group_updated" => Self::GroupUpdated,
+            text::TextCodec::TYPE_ID => Self::Text,
+            membership_change::GroupMembershipChangeCodec::TYPE_ID => Self::GroupMembershipChange,
+            group_updated::GroupUpdatedCodec::TYPE_ID => Self::GroupUpdated,
             _ => Self::Unknown,
         }
     }
 
     pub fn to_string(&self) -> &'static str {
         match self {
             Self::Unknown => "unknown",
-            Self::Text => "text",
-            Self::GroupMembershipChange => "group_membership_change",
-            Self::GroupUpdated => "group_updated",
+            Self::Text => text::TextCodec::TYPE_ID,
+            Self::GroupMembershipChange => membership_change::GroupMembershipChangeCodec::TYPE_ID,
+            Self::GroupUpdated => group_updated::GroupUpdatedCodec::TYPE_ID,
         }
     }
 }

xmtp_content_types/src/membership_change.rs

@@ -12,7 +12,7 @@ pub struct GroupMembershipChangeCodec {}
 
 impl GroupMembershipChangeCodec {
     const AUTHORITY_ID: &'static str = "xmtp.org";
-    const TYPE_ID: &'static str = "group_membership_change";
+    pub const TYPE_ID: &'static str = "group_membership_change";
 }
 
 impl ContentCodec<GroupMembershipChanges> for GroupMembershipChangeCodec {

xmtp_content_types/src/text.rs

@@ -8,7 +8,7 @@ pub struct TextCodec {}
 
 impl TextCodec {
     const AUTHORITY_ID: &'static str = "xmtp.org";
-    const TYPE_ID: &'static str = "text";
+    pub const TYPE_ID: &'static str = "text";
     const ENCODING_KEY: &'static str = "encoding";
     const ENCODING_UTF8: &'static str = "UTF-8";
 }