feat(tvldb): Import the tvldb/paroxysm source, add a Nix derivation

- This imports the tvldb (actually a thing called 'paroxysm') code
  from https://git.theta.eu.org/eta/paroxysm into the monorepo.
- Additionally, I did a nix thing, yay! \o/
  (well, with tazjin's help)
- 3p/default.nix needed modifying to whitelist pgsql.

Change-Id: Icdf13ca221650dde376f632bd2dd8a087af451bf
Reviewed-on: https://cl.tvl.fyi/c/depot/+/389
Reviewed-by: tazjin <mail@tazj.in>

fun/tvldb/src/cfg.rs

@@ -0,0 +1,11 @@
+use std::collections::HashSet;
+
+#[derive(Deserialize)]
+pub struct Config {
+    pub database_url: String,
+    pub irc_config_path: String,
+    #[serde(default)]
+    pub admins: HashSet<String>,
+    #[serde(default)]
+    pub log_filter: Option<String>,
+}