Remove the CrowdSec decision feed (closes #315)

sneak ruled to remove it. Gone: the heuristic crowdsec, the ban cause
crowdsec and its earlier_bans count, the tag crowdsec, the settings
SWW_WAF_CROWDSEC_LAPI_URL and SWW_WAF_CROWDSEC_LAPI_KEY, the decision
list fetch and parse in internal/reputation, their tests, and every
mention in the README, SPEC.md and docs/. EVALUATION.md keeps its
comparison of tools.

The ban ledger's internal ban function loses its expires parameter,
which only CrowdSec bans used.

Model: opus-5-5

SPEC.md

@@ -176,7 +176,6 @@ field gives that name. `refusal_limit` and `byte_limits` give theirs in
 8. The reputation sources (see "Reputation"), in this order:
     - A client on a fetched blocklist gets `SWW_WAF_BLOCKLIST_ACTION`
       (`blocklists`).
-    - A client on the CrowdSec decision list is banned (`crowdsec`).
     - A client listed by a DNS blocklist gets `SWW_WAF_DNSBL_ABUSEIPDB_ACTION`
       (`dnsbl`).
     - A client scored at least `SWW_WAF_ABUSEIPDB_MIN_SCORE` by AbuseIPDB gets
@@ -301,14 +300,6 @@ without a ban, because the Core Rule Set has false positives. A `block` rule
 does the same. Those refusals count toward the refusal limit, so a client that
 keeps setting them off is banned for a broken limit.
 
-A client on the CrowdSec decision list is banned until the decision ends, with
-the cause `crowdsec`. Only a client that sends a request is banned, so a long
-list does not fill `bans.json`. Such a ban is never made permanent. It does not
-make the netblock's next ban for a broken limit longer. A ban lifted while the
-decision is in force is made again at the client's next request. To lift it for
-good, delete the decision in CrowdSec, then lift the ban once the list has been
-fetched again.
-
 These refuse each request they cover, record nothing in `bans.json`, and count
 no offence:
 
@@ -338,10 +329,10 @@ toward `SWW_WAF_MAX_BANS`, so such bans can never fill the table.
 
 A request refused under a ban that runs out is logged with the action
 `temporarily_banned`. Under a permanent ban the action is `permanently_banned`.
-A request refused for a clear sign of attack or a CrowdSec decision takes the
-action for the ban it made. A request that makes a ban permanent is logged as
-`permanently_banned`. A request over a rate limit is logged as
-`client_is_rate_limited`, whichever ban it makes.
+A request refused for a clear sign of attack takes the action for the ban it
+made. A request that makes a ban permanent is logged as `permanently_banned`. A
+request over a rate limit is logged as `client_is_rate_limited`, whichever ban
+it makes.
 
 ## Settings
 
@@ -575,9 +566,9 @@ Each tag and where it comes from:
 - One tag per list of `SWW_WAF_TAG_LISTS` that holds the client (`tag_lists`),
   the tag being the list's name, such as `torexit` or `vpn=mullvad`. These lists
   are fetched and kept like a blocklist. `waf` ships none of its own.
-- `crowdsec`, `dnsbl=<zone>` and `abuseipdb`, when that reputation source lists
-  the client, whatever the source's action. A zone with a key is named with the
-  key masked, as the `reputation` field gives it.
+- `dnsbl=<zone>` and `abuseipdb`, when that reputation source lists the client,
+  whatever the source's action. A zone with a key is named with the key masked,
+  as the `reputation` field gives it.
 - `exploitsignature`, when a rule file or the Core Rule Set matched the request.
   For the Core Rule Set a match is a score at or over
   `SWW_WAF_CORE_RULE_SET_SCORE_THRESHOLD`.
@@ -1960,12 +1951,11 @@ to the surrounding netblock. The four ban lengths are under "Bans".
 ### Reputation
 
 No source is on by default. A source acts on a list kept elsewhere; the defaults
-judge a client only by what it does here. AbuseIPDB and CrowdSec also need an
-account or an engine of the operator's own. The list best suited to be on by
-default, Spamhaus DROP, has terms, below, that forbid frequent fetching, and
-Spamhaus may block an address that breaks them. Each `waf` fetches its own copy,
-so several of them on one host, sharing one address, would often fetch too close
-together.
+judge a client only by what it does here. AbuseIPDB also needs an account of the
+operator's own. The list best suited to be on by default, Spamhaus DROP, has
+terms, below, that forbid frequent fetching, and Spamhaus may block an address
+that breaks them. Each `waf` fetches its own copy, so several of them on one
+host, sharing one address, would often fetch too close together.
 
 - Blocklists (`SWW_WAF_BLOCKLIST_URLS`) are text files of addresses and
   netblocks, one to a line, as the Spamhaus DROP list is written. Anything after
@@ -1998,18 +1988,6 @@ together.
   percentage of every request and byte limit, and suits a list of addresses
   shared with ordinary visitors, such as Tor exits. `log` only notes the hit in
   the log line and raises an alert.
-- A CrowdSec engine on the host (`SWW_WAF_CROWDSEC_LAPI_URL`) has its decision
-  list fetched every minute, with `SWW_WAF_CROWDSEC_LAPI_KEY` in the `X-Api-Key`
-  header. The list is kept like a fetched blocklist, and a client on it is
-  banned (see "Bans"). Only decisions of the type `ban` on an address or a
-  netblock are used; any other, such as a captcha or a country, is left out. A
-  decision lasts for the `duration` it had left when the engine answered. This
-  is how a fleet-wide blocklist can arrive without `waf` depending on CrowdSec.
-  A fetch fails when:
-    - the engine answers other than `200`, a redirect included;
-    - the fetch does not finish within a minute;
-    - the answer is longer than 16 MiB;
-    - the answer is not a list of decisions.
 - Each DNS blocklist (`SWW_WAF_DNSBL_ZONES`) is asked about a client's own
   address in the background, the first time the client is seen. No request waits
   for the answer. The name asked about is the one RFC 5782 gives: the numbers of
@@ -2437,14 +2415,13 @@ client without an answer by then counts as unknown. No question waits on these,
 which run in the background:
 
 - the DNS blocklists and AbuseIPDB;
-- fetching the blocklists, the tag lists, the CrowdSec decision list and the
-  file `SWW_WAF_ASN_LIMIT_PERCENT_URL` names.
+- fetching the blocklists, the tag lists and the file
+  `SWW_WAF_ASN_LIMIT_PERCENT_URL` names.
 
 In `enforce` mode, a question does not wait for GeoJS when it is a request:
 
 - from a client on a fetched blocklist, while `SWW_WAF_BLOCKLIST_ACTION` is
   `deny`;
-- from a client on the CrowdSec decision list;
 - that would take its client over a rate limit at 100% of it, since a percentage
   can only lower a limit.