Implement User handling and authentication

New struct: User, corresponds to a student

Blocks and users are persistent (written to a text file)

PostgreSQL would've been overkill, we have 30 students

AuthRequest is the representation for incoming register requests and
User is the inner representation

Students who are enrolled to the class are hardcoded, only they can
register new accounts

There are two new tests, one checks if a priviliged (=enrolled) user can
create an account and the other checks if a unpriviliged one cannot

There are quick verbose error messages that I'm not married to, might
move on to something better honestly

There's nothing stopping a malicious user to pre-register everyone with
mock public keys and effectively lock everyone out, what's a good secret
we can use?

1 files changed, 3 insertions, 2 deletions

diff --git a/Cargo.toml b/Cargo.toml
index a203a6f..2ae2b25 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,7 +14,8 @@ chrono = { version = "0.4.10", features = ["serde"] }
 log = "0.4.8"
 pretty_env_logger = "0.3.1"
 parking_lot = "0.10.0"
+serde_json = "1.0.59"
+lazy_static = "1.4.0"
 
 [dev-dependencies]
-serde_json = "1.0.44"
-serde_test = "1.0.104"
+serde_test = "1.0.117"