Make the home page's AS name search work (closes #151)

The AS Name Search card on the home page said the search was coming
soon. It now asks the new GET /api/v1/search/as?q=<text>, which
searches the AS list built into asinfo, and lists the matches as links
to their AS pages. An empty q answers 400. asinfo.Search now ignores
case and returns its matches in AS number order. asinfo lowers each
handle and description once, when the list loads.

A match can be an AS that the database has no record of. Its AS page
and /api/v1/as/{asn} then take its handle and description from asinfo
and still list its prefixes. They answer 404 only for an AS with no
record, no asinfo entry and no prefix. Empty prefix lists in that JSON
answer are [] rather than null.

Model: opus-5-5

README.md

@@ -56,15 +56,17 @@ Every route answers `HEAD` as it answers `GET`, without the body.
 
 ### Web Interface
 
-- `GET /` - Home page (HTML): headline figures, and lookups by AS number and by
-  IP address
+- `GET /` - Home page (HTML): headline figures, lookups by AS number and by IP
+  address, and a search of AS names
 - `GET /status` - HTML status dashboard, which reads `/api/v1/stats`
 - `GET /status.json` - JSON statistics: feed, memory, database and route figures
 - `GET /.well-known/healthcheck.json` - Health check (JSON): 200 when the
   database answers and the RIS Live feed is connected, otherwise 503;
   `data.status` is `ok` or `error` and `data.checks` says which check failed
 - `GET /as/{asn}` - AS detail page (HTML): the prefixes the AS originates and
-  its peers
+  its peers. When the database has no record of the AS, its handle and
+  description come from the AS list built into RouteWatch. The page then shows
+  no first-seen date.
 - `GET /prefix/{prefix}/{length}` - Prefix detail page (HTML), such as
   `/prefix/192.0.2.0/24`: every live route for the prefix, one per peer, and its
   origin ASes
@@ -93,9 +95,22 @@ Every route answers `HEAD` as it answers `GET`, without the body.
   and 404 when none of the addresses has a live route. A PTR lookup gets 2
   seconds; an address whose lookup takes longer is answered without PTR names.
 - `GET /api/v1/as/{asn}` - The AS and the prefixes it originates, IPv4 and IPv6
-  apart, each with when its newest route was updated
+  apart, each with when its newest route was updated. When the database has no
+  record of the AS, its handle and description come from the AS list built into
+  RouteWatch. The answer then has no `first_seen` or `last_seen`.
 - `GET /api/v1/prefix/{prefix}/{length}` - Every live route for the prefix, one
   per peer, and the same routes grouped by origin AS in `origins`
+- `GET /api/v1/search/as?q={text}` - Finds the ASes whose handle or description
+  contains `{text}`, ignoring case. `data` holds:
+    - `query`: `{text}` without its leading and trailing spaces
+    - `total`: the number of ASes that match
+    - `results`: the first 50 of them in AS number order, each with `asn`,
+      `handle` and `description`
+
+    The search reads the AS list built into RouteWatch, not the database. The
+    list comes from [ipverse/asn-info](https://github.com/ipverse/asn-info). A
+    match can therefore be an AS that the database has no record of. A `q` that
+    is missing, empty or only spaces answers 400.
 
 A JSON answer is `{"status": "ok", "data": ...}`, or for an error
 `{"status": "error", "error": {"msg": ..., "code": ...}}`, and carries an
@@ -106,13 +121,15 @@ took. The health check is the exception: its 503 answer is also
 A request that runs past its time limit answers 504: the limit is 30 seconds,
 and 4 seconds for the database reads behind `/status.json` and `/api/v1/stats`.
 An AS number, prefix or mask length that does not parse answers 400, as does a
-mask length out of range for its IP version. An AS the database does not hold,
-or a prefix with no live route, answers 404. The HTML pages give these errors as
-plain text. Under `/api/v1` and `/ip/`, a path no route matches answers 404 with
-the message `Not found`, and `POST`, `PUT`, `PATCH`, `DELETE`, `OPTIONS`,
-`TRACE` or `CONNECT` answers 405 with `Method not allowed`. A 500 answer says
-only `Internal server error`, and a host name that does not resolve only
-`could not resolve host name`; the detail goes to the log.
+mask length out of range for its IP version. An AS answers 404 when it is not in
+the AS list built into RouteWatch and the database has neither a record of it
+nor a live route it originates. A prefix with no live route answers 404 too. The
+HTML pages give these errors as plain text. Under `/api/v1` and `/ip/`, a path
+no route matches answers 404 with the message `Not found`, and `POST`, `PUT`,
+`PATCH`, `DELETE`, `OPTIONS`, `TRACE` or `CONNECT` answers 405 with
+`Method not allowed`. A 500 answer says only `Internal server error`, and a host
+name that does not resolve only `could not resolve host name`; the detail goes
+to the log.
 
 Every answer carries `Strict-Transport-Security`, `Content-Security-Policy`,
 `X-Frame-Options`, `X-Content-Type-Options`, `Referrer-Policy` and