Add support for MFA with Duo's Universal Prompt (#4637)

* Add initial working Duo Universal Prompt support.

* Add db schema and models for Duo 2FA state storage

* store duo states in the database and validate during authentication

* cleanup & comments

* bump state/nonce length

* replace stray use of TimeDelta

* more cleanup

* bind Duo oauth flow to device id, drop redundant device type handling

* drop redundant alphanum string generation code

* error handling cleanup

* directly use JWT_VALIDITY_SECS constant instead of copying it to DuoClient instances

* remove redundant explicit returns, rustfmt

* rearrange constants, update comments, error message

* override charset on duo state column to ascii for mysql

* Reduce twofactor_duo_ctx state/nonce column size in postgres and maria

* Add fixes suggested by clippy

* rustfmt

* Update to use the make_http_request

* Don't handle OrganizationDuo

* move Duo API endpoint fmt strings out of macros and into format! calls

* Add missing indentation

Co-authored-by: Daniel García <dani-garcia@users.noreply.github.com>

* remove redundant expiry check when purging Duo contexts

---------

Co-authored-by: BlackDex <black.dex@gmail.com>
Co-authored-by: Daniel García <dani-garcia@users.noreply.github.com>

migrations/mysql/2024-06-05-131359_add_2fa_duo_store/up.sql

@@ -0,0 +1,8 @@
+CREATE TABLE twofactor_duo_ctx (
+    state      VARCHAR(64)  NOT NULL,
+    user_email VARCHAR(255) NOT NULL,
+    nonce      VARCHAR(64)  NOT NULL,
+    exp        BIGINT       NOT NULL,
+
+    PRIMARY KEY (state)
+);