feat: Basic domain creation API

src/db/error.rs

@@ -6,6 +6,7 @@ pub type BoxedError = Box<dyn std::error::Error + Send + Sync + 'static>;
 
 #[derive(Debug)]
 pub enum UserCreationError {
+    DomainNotFound(String),
     UserAlreadyExists(UserRef),
     Permissions,
 }
@@ -13,6 +14,7 @@ pub enum UserCreationError {
 impl fmt::Display for UserCreationError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
+            Self::DomainNotFound(domain) => write!(f, "No domain {domain} to create user in"),
             Self::UserAlreadyExists(user) => write!(f, "User already exists: {user}"),
             Self::Permissions => write!(f, "You do not have permissions to create this user"),
         }
@@ -20,3 +22,25 @@ impl fmt::Display for UserCreationError {
 }
 
 impl std::error::Error for UserCreationError {}
+
+#[derive(Debug)]
+pub enum DomainCreationError {
+    DomainAlreadyExists(String),
+    InvalidDomain(String),
+}
+
+impl fmt::Display for DomainCreationError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::DomainAlreadyExists(domain) => {
+                write!(f, "Cannot create domain {domain} because it already exists")
+            }
+            Self::InvalidDomain(domain) => write!(
+                f,
+                "Cannot create domain `{domain}` because it's not considered a valid domain"
+            ),
+        }
+    }
+}
+
+impl std::error::Error for DomainCreationError {}