Backend work to support minimum password complexity (#2965)

* config: Add minimum password complexity option

* PasswordManager: add function for checking if complexity is sufficient

* Enforce password complexity on registration, change and recovery

* cli: Use exit code 1 for weak passwords

This seems preferable to exit code 0, but ideally we should choose one
and document it.

* Expose minimum password complexity score over GraphQL

crates/data-model/src/site_config.rs

@@ -78,4 +78,8 @@ pub struct SiteConfig {
 
     /// Captcha configuration
     pub captcha: Option<CaptchaConfig>,
+
+    /// Minimum password complexity, between 0 and 4.
+    /// This is a score from zxcvbn.
+    pub minimum_password_complexity: u8,
 }