Big repository reorganization

The code is divided in three crates:
- plume-common, for the ActivityPub module, and some common utils
- plume-models, for the models and database-related code
- plume, the app itself

This new organization will allow to test it more easily, but also to create other tools that only reuse a little part of
the code (for instance a Wordpress import tool, that would just use the plume-models crate)

plume-common/src/activity_pub/request.rs

@@ -0,0 +1,52 @@
+use base64;
+use openssl::hash::{Hasher, MessageDigest};
+use reqwest::{
+    mime::Mime,
+    header::{ContentType, Date, Headers, UserAgent}
+};
+use std::{
+    str::FromStr,
+    time::SystemTime
+};
+
+use activity_pub::sign::Signer;
+
+const USER_AGENT: &'static str = "Plume/0.1.0";
+
+header! {
+    (Signature, "Signature") => [String]
+}
+
+header! {
+    (Digest, "Digest") => [String]
+}
+
+pub fn headers() -> Headers {
+    let mut headers = Headers::new();
+    headers.set(UserAgent::new(USER_AGENT));
+    headers.set(Date(SystemTime::now().into()));
+    headers.set(ContentType(Mime::from_str("application/activity+json").unwrap()));
+    headers
+}
+
+pub fn signature<S: Signer>(signer: &S, headers: Headers) -> Signature {
+    let signed_string = headers.iter().map(|h| format!("{}: {}", h.name().to_lowercase(), h.value_string())).collect::<Vec<String>>().join("\n");
+    let signed_headers = headers.iter().map(|h| h.name().to_string()).collect::<Vec<String>>().join(" ").to_lowercase();
+    
+    let data = signer.sign(signed_string);
+    let sign = base64::encode(&data[..]);
+
+    Signature(format!(
+        "keyId=\"{key_id}\",algorithm=\"rsa-sha256\",headers=\"{signed_headers}\",signature=\"{signature}\"",
+        key_id = signer.get_key_id(),
+        signed_headers = signed_headers,
+        signature = sign
+    ))
+}
+
+pub fn digest(body: String) -> Digest {
+    let mut hasher = Hasher::new(MessageDigest::sha256()).unwrap();
+    hasher.update(&body.into_bytes()[..]).unwrap();
+    let res = base64::encode(&hasher.finish().unwrap());
+    Digest(format!("SHA-256={}", res))
+}