Reimplement most of the tool:

Most of the tool has been reimplemented, with the exception of the
permission editing feature, which is currently half implemented. There
are also several TODOs spread around that would benefit from some action

src/core/common.rs

@@ -0,0 +1,91 @@
+use anyhow::Context;
+use indoc::indoc;
+use itertools::Itertools;
+use nix::unistd::{getuid, Group, User};
+use std::ffi::CString;
+
+pub fn get_current_unix_user() -> anyhow::Result<User> {
+    User::from_uid(getuid())
+        .context("Failed to look up your UNIX username")
+        .and_then(|u| u.ok_or(anyhow::anyhow!("Failed to look up your UNIX username")))
+}
+
+pub fn get_unix_groups(user: &User) -> anyhow::Result<Vec<Group>> {
+    let user_cstr =
+        CString::new(user.name.as_bytes()).context("Failed to convert username to CStr")?;
+    let groups = nix::unistd::getgrouplist(&user_cstr, user.gid)?
+        .iter()
+        .filter_map(|gid| {
+            match Group::from_gid(*gid).map_err(|e| {
+                log::trace!(
+                    "Failed to look up group with GID {}: {}\nIgnoring...",
+                    gid,
+                    e
+                );
+                e
+            }) {
+                Ok(Some(group)) => Some(group),
+                _ => None,
+            }
+        })
+        .collect::<Vec<Group>>();
+
+    Ok(groups)
+}
+
+pub fn validate_prefix_for_user<'a>(name: &'a str, user: &User) -> anyhow::Result<&'a str> {
+    let user_groups = get_unix_groups(user)?;
+
+    let mut split_name = name.split('_');
+
+    let prefix = split_name
+        .next()
+        .ok_or(anyhow::anyhow!(indoc! {r#"
+              Failed to find prefix.
+            "#},))
+        .and_then(|prefix| {
+            if user.name == prefix || user_groups.iter().any(|g| g.name == prefix) {
+                Ok(prefix)
+            } else {
+                anyhow::bail!(
+                    indoc! {r#"
+                      Invalid prefix: '{}' does not match your username or any of your groups.
+                      Are you sure you are allowed to create databases or users with this prefix?
+
+                      Allowed prefixes:
+                        - {}
+                      {}
+                    "#},
+                    prefix,
+                    user.name,
+                    user_groups
+                        .iter()
+                        .filter(|g| g.name != user.name)
+                        .map(|g| format!("  - {}", g.name))
+                        .sorted()
+                        .join("\n"),
+                );
+            }
+        })?;
+
+    if !split_name.next().is_some_and(|s| !s.is_empty()) {
+        anyhow::bail!(
+            indoc! {r#"
+              Missing the rest of the name after the user/group prefix.
+
+              The name should be in the format: '{}_<name>'
+            "#},
+            prefix
+        );
+    }
+
+    Ok(prefix)
+}
+
+pub fn quote_literal(s: &str) -> String {
+    format!("'{}'", s.replace('\'', r"\'"))
+}
+
+pub fn quote_identifier(s: &str) -> String {
+    format!("`{}`", s.replace('`', r"\`"))
+}