Replace environment, restHost and realtimeHost with endpoint - #1249

@coderabbitai please check how mandatory is this with respect to spec and rest of the code, check if current fix is enough, accordingly expand on the above

#!/bin/bash
ast-grep outline lib/src/main/java/io/ably/pubsub/http/HttpUtils.java --items all
ast-grep outline lib/src/main/java/io/ably/pubsub/transport/WebSocketTransport.java --items all
ast-grep outline lib/src/test/java/io/ably/pubsub/http/HttpUtilsTest.java --items all
rg -n -C3 'hostForUrl|buildURL\(|new URI\(|new URL\(|InetSocketAddress\(|getHost\(' lib/src/main/java --glob '*.java'
rg -n -C3 'REC1b2|ADR.?119|::1|IPv6' --glob '*.java' --glob '*.md' --glob '*gradle*'

#!/bin/bash
sed -n '185,220p' lib/src/main/java/io/ably/pubsub/http/HttpUtils.java
sed -n '110,160p' lib/src/main/java/io/ably/pubsub/transport/WebSocketTransport.java
ast-grep outline lib/src/main/java/io/ably/pubsub/http/HttpCore.java --items all --match 'httpExecute|retry|Retry'
rg -n -C4 'getHost\(|getAuthority\(|InetSocketAddress\(|URI\.create\(|new URI\(|new URL\(|wsUri|setHost\(' --glob '*.java' --glob '*.kt' -g '!**/test/**' -g '!**/androidTest/**'
fd -i 'WebSocket|HttpEngine|HttpClient|ProxySocket'
gh api repos/ably/ably-common/contents --jq '.[].name'

#!/bin/bash
ast-grep outline lib/src/main/java/io/ably/pubsub/http/HttpCore.java --items all
rg -n -C5 'buildURL|url\.|new HttpRequest|preferred|fallback|host =' lib/src/main/java/io/ably/pubsub/http/HttpCore.java
for file in network-client-okhttp/src/main/java/io/ably/pubsub/network/OkHttpEngine.java network-client-okhttp/src/main/java/io/ably/pubsub/network/OkHttpWebSocketEngine.java lib/src/test/java/io/ably/pubsub/transport/WebSocketTransportTest.java; do
  ast-grep outline "$file" --items all
done
rg -n -C4 '\.url\(|create\(|IPv6|::1|ws://|wss://' network-client-okhttp/src/main/java/io/ably/pubsub/network/OkHttpEngine.java network-client-okhttp/src/main/java/io/ably/pubsub/network/OkHttpWebSocketEngine.java lib/src/test/java/io/ably/pubsub/transport/WebSocketTransportTest.java
gh api 'repos/ably/ably-common/git/trees/main?recursive=1' --jq '.tree[].path' | grep -Ei 'spec|feature|119|endpoint'

@sacOO7 IPv6 bracketing is required for valid transport URLs. The current fix is sufficient for the URL-formatting defect identified above. An actual IPv6 request and connection test would add confidence, but I would not make those tests mandatory for this fix.

Specification requirement

The endpoint contract supplied for this PR treats values containing :: as hostnames and preserves them unchanged. Therefore, Defaults.getPrimaryDomain("::1") returning "::1" is correct. Do not add brackets in Defaults.

When a transport places that address in a URL, RFC 3986, Section 3.2.2 requires brackets:

Raw host:      ::1
REST URL:      http://[::1]:8080/time
WebSocket URL: ws://[::1]:8080/

This is a URL syntax requirement, not an optional formatting choice. I could not independently retrieve the authoritative REC1/ADR-119 text, so the Ably-specific conclusion relies on the endpoint contract supplied here.

Current implementation

I verified these paths:

• HttpUtils.hostForUrl brackets colon-containing hosts and preserves already-bracketed hosts.
• HttpUtils.buildURL applies the helper when constructing REST endpoint URLs.
• WebSocketTransport.connect applies the same helper before passing the URL to the WebSocket engine.
• The default WebSocket engine uses URI.create(url). The OkHttp WebSocket engine passes the URL to Request.Builder.url(url).
• Host selection retains the original host. WebSocketTransport.getHost() still returns params.host.

The fix therefore operates at the correct boundary. It covers HTTP/HTTPS and WS/WSS without changing host comparisons. No further change to Defaults.java is needed for this finding.

Test coverage

HttpUtilsTest covers unbracketed IPv6, already-bracketed IPv6, unchanged non-IPv6 hosts, and HTTP URL host/port parsing.

The most useful small addition would be a mocked WebSocketTransport test that asserts the URL passed to WebSocketEngine.create contains [::1], while getHost() remains "::1".

Real IPv6 loopback tests would check network-engine behavior beyond URL construction. They are useful additional coverage, but the evidence available does not establish them as a specification requirement or a blocker for this formatting fix.

This assessment is source-level verification. I did not run the tests or establish end-to-end IPv6 connectivity.

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@coderabbitai so we are good with current changes right?

@sacOO7 Yes—the current changes are sufficient for this IPv6 URL-formatting issue, based on the source review.

Keep Defaults.getPrimaryDomain("::1") unchanged. The REST and WebSocket URL builders now add the required brackets.

Additional WebSocket or IPv6 loopback tests are optional coverage, not blockers for this fix. This does not establish end-to-end IPv6 connectivity or approval of the entire PR.

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