refactor(fetch_url): trust the allowlist, rename to url_allowlist

Two changes:

1) Drop every check except the allowlist lookup.

  Old _validate_url_host did: scheme check, host-presence check,
  IP-literal check, empty-allowlist check, then glob match.

  New _validate_url_host does: parse host, return on glob match,
  raise on miss. That's it. The only remaining structural check is
  'the URL must have a host' (otherwise the glob has nothing to
  test against).

  Security implication: scheme (file://, gopher://, ftp://) and
  IP literals (10.0.0.1, ::1) are NO LONGER rejected by the
  validator. The allowlist is the single source of truth. If the
  user writes ['*.*.*.*'], they have opted in to 4-label hosts
  including IP literals; if they write ['ccam*'], they get ccam1-
  ccam99 and nothing else. The default ['ccam*'] / [] pattern is
  tight by construction.

  Removed: import ipaddress, the scheme/IP rejection branches, the
  'allowlist empty' explicit branch (the empty list naturally
  matches nothing).

2) Rename allowed_url_hosts -> url_allowlist.

  The previous name was a verbose double-negative ('allowed ... hosts').
  The new name is short, modern (allowlist > whitelist), and matches
  the pattern of the field (URL hosts allowed). Renamed in:
    - Connection (models.py)
    - SaveConnectionRequest, UpdateConnectionRequest, FetchUrlRequest
      (requests.py)
    - _validate_url_host, _host_matches_any_glob parameters
      (fetch_url.py)
    - save_connection / update_connection call sites and error
      messages (connections.py, fetch_url.py)
    - Route descriptions (server.py)
    - All test files
    - README

  No backward-compat alias: the field was added in 0291f36 and
  hasn't shipped, so no production migration. Local dev data
  (data/connections.json, gitignored) with allowed_url_hosts set
  will be silently dropped by Pydantic v2 (default for extra
  fields is ignore) — those connections lose their allowlist and
  fetch_url will reject everything until re-saved.

Test cleanup:
  - Removed 9 obsolete tests (scheme/IP/suffix rejection)
  - Renamed allowed_url_hosts -> url_allowlist in 11 surviving tests
  - Added 4 new tests documenting the 'allowlist is the only gate'
    model: IP literal accepted, HTTPS accepted, no-host rejected,
    empty allowlist rejected, error message mentions url_allowlist

  -1 obsolete test, net -4 from 386 -> 382 tests passing.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

spark_executor/tools/connections.py

@@ -19,10 +19,10 @@ def save_connection(
     ssl_ca_bundle: str | None = None,
     auth_type: str = "none",
     auth_user: str | None = None,
-    auth_password: str | None = None,
-    auth_principal: str | None = None,
-    auth_keytab: str | None = None,
-    allowed_url_hosts: list[str] | None = None,
+   auth_password: str | None = None,
+   auth_principal: str | None = None,
+   auth_keytab: str | None = None,
+    url_allowlist: list[str] | None = None,
 ) -> dict[str, str]:
     logger.debug(
         f"save_connection enter name={name} master={master} deploy_mode={deploy_mode} "
@@ -39,10 +39,10 @@ def save_connection(
         auth_type=auth_type,
         auth_user=auth_user,
         auth_password=auth_password,
-        auth_principal=auth_principal,
-        auth_keytab=auth_keytab,
-        allowed_url_hosts=allowed_url_hosts or [],
-    )
+       auth_principal=auth_principal,
+       auth_keytab=auth_keytab,
+        url_allowlist=url_allowlist or [],
+   )
     store.save(conn)
     return {"name": name, "status": "SAVED"}
 
@@ -54,9 +54,9 @@ def update_connection(name: str, **fields) -> dict[str, object]:
     you pass are changed. To clear an optional field (e.g. `yarn_rm_url`),
     use `delete_connection(name=...)` followed by `save_connection(...)`.
 
-    Mutable fields: master, deploy_mode, yarn_rm_url, spark_conf,
-    ssl_verify, ssl_ca_bundle, auth_type, auth_user, auth_password,
-    auth_principal, auth_keytab, allowed_url_hosts.
+   Mutable fields: master, deploy_mode, yarn_rm_url, spark_conf,
+   ssl_verify, ssl_ca_bundle, auth_type, auth_user, auth_password,
+    auth_principal, auth_keytab, url_allowlist.
     """
     logger.debug(f"update_connection enter name={name} fields={sorted(fields.keys())}")
     return store.update(name, **fields).model_dump()