Fix async redirect handling regression from FOLLOW_REDIRECTS default

[cursor]

Restores async-mode redirect interception behavior that was accidentally regressed in #1278.

Fixes

• Async connectors (e.g. Slack Analytics, ChatGPT Enterprise) that rely on intercepting 3xx responses when FOLLOW_REDIRECTS is not configured

Change implications

• dependencies added/changed? no
• something important to note in future release notes?
  • yes: Adding property config for redirect #1278 changed the default redirect-following behavior for async API connectors. When FOLLOW_REDIRECTS is unset, redirects are now again disabled in async mode (restoring pre-Adding property config for redirect #1278 behavior) so the proxy can manually fetch from the Location header. Only ChatGPT Enterprise had an explicit FOLLOW_REDIRECTS=FALSE override in Terraform; other async connectors like Slack Analytics were affected.
  • breaking changes? no — this restores the intended behavior from Handle redirection with async #1236

Bug and impact

Commit #1278 (Added property) changed ApiDataRequestHandler to default FOLLOW_REDIRECTS to true for all requests, replacing the prior behavior of setFollowRedirects(!processingContext.getAsync()). Async connectors such as Slack Analytics depend on the proxy intercepting 3xx responses and manually fetching from the Location URL (with HTTPS validation). With auto-follow enabled, that interception block is bypassed, breaking async data collection for connectors that do not have an explicit FOLLOW_REDIRECTS=FALSE environment variable.

Root cause

#1278 introduced a configurable FOLLOW_REDIRECTS property but changed the default from context-aware (false in async mode) to unconditionally true, removing the async-specific redirect handling added in #1236.

Fix and validation

• Restore orElse(!processingContext.getAsync()) as the default when FOLLOW_REDIRECTS is unset
• Update ProxyConfigProperty javadoc to document the async/sync default difference
• Add asyncModeDisablesRedirectFollowingByDefault unit test
• Ran mvn test -pl core -am -Dtest=ApiDataRequestHandlerTest#asyncModeDisablesRedirectFollowingByDefault,ApiDataRequestHandlerTest#handleShouldFollowRedirectManuallyInAsyncMode,ApiDataRequestHandlerTest#handleShouldLetHttpClientFollowRedirectInSyncMode — all pass