added database crate, "settings" with migrations and queries, running migrations on web startup

crates/database/src/error.rs

@@ -0,0 +1,45 @@
+// error
+#[derive(thiserror::Error)]
+// the rest
+#[derive(Debug)]
+pub enum Error {
+    #[error("Unique constraint on primary key")]
+    UniqueConstraintPrimaryKey,
+
+    #[error("Unique constraint on key {0}")]
+    UniqueConstraint(String),
+
+    #[error("{0}")]
+    Database(#[from] sqlx::Error),
+}
+
+fn parse_unique_constraint(msg: &str) -> Option<String> {
+    // Format will be "table.column"
+    let mut constraint = msg.strip_prefix("UNIQUE constraint failed: ")?.split('.');
+
+    // Extract "column" (which is the second value)
+    let _table = constraint.next()?;
+    let column = constraint.next()?;
+
+    Some(column.to_string())
+}
+
+pub fn handle_error(e: sqlx::Error) -> Error {
+    match e.as_database_error() {
+        Some(database_error) => match database_error.code() {
+            // List of all codes: https://www.sqlite.org/rescode.html
+            Some(code) => match code.as_ref() {
+                "1555" => Error::UniqueConstraintPrimaryKey,
+
+                // Attempt to extract unique constraint column
+                "2067" => match parse_unique_constraint(database_error.message()) {
+                    Some(column) => Error::UniqueConstraint(column),
+                    None => Error::Database(e),
+                },
+                _ => Error::Database(e),
+            },
+            None => Error::Database(e),
+        },
+        None => Error::Database(e),
+    }
+}