feat(auth): finish protocol 10 method 2 and 3

src/rmc/structures/rmc_struct.rs

@@ -0,0 +1,24 @@
+use std::io::Write;
+use bytemuck::bytes_of;
+use crate::rmc::structures::Result;
+
+#[repr(C, packed)]
+struct StructureHeader{
+    version: u8,
+    length: u32
+}
+
+pub fn write_struct(mut writer: &mut dyn Write, version: u8, pred: impl Fn(&mut Vec<u8>)) -> Result<()> {
+    writer.write_all(&[version])?;
+
+    let mut scratch_space: Vec<u8> = Vec::new();
+
+    (pred)(&mut scratch_space);
+
+    let u32_size= scratch_space.len() as u32;
+
+    writer.write_all(bytes_of(&u32_size))?;
+    writer.write_all(&scratch_space)?;
+
+    Ok(())
+}