Update Context to accept External Identity Provider. (#127)

* rename .account_id() to .id()

* Create logos-traits crate

* Remove AccountId references

* external IdentityProvider for Context

* Fix compile errors from merge

* Update logos-traits to shared-traits

* format fixes

* warnings cleanup

* clippy fix

* Remove rebase artifact

core/shared-traits/src/lib.rs

@@ -0,0 +1,39 @@
+use crypto::{Ed25519Signature, Ed25519VerifyingKey};
+use std::fmt;
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct IdentId(String);
+pub type IdentIdRef<'a> = &'a IdentId;
+
+impl IdentId {
+    pub fn new(id: impl Into<String>) -> Self {
+        Self(id.into())
+    }
+
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+}
+
+impl fmt::Display for IdentId {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        std::fmt::Display::fmt(&self.0, f)
+    }
+}
+
+impl AsRef<str> for IdentId {
+    fn as_ref(&self) -> &str {
+        &self.0
+    }
+}
+
+/// Represents an external Identity
+/// Implement this to provide an Authentication model for users/installations
+pub trait IdentityProvider {
+    fn id(&self) -> IdentIdRef<'_>;
+    // Display name is not garenteed to be consistent. It should only be used to
+    // provded a more readable identifier for the account.
+    fn display_name(&self) -> String;
+    fn sign(&self, payload: &[u8]) -> Ed25519Signature;
+    fn public_key(&self) -> &Ed25519VerifyingKey;
+}