fix(yes-core): honour prefix for array values in HashUtils.deep_flatten_hash

[aroeczek]

What

Yes::Core::Utils::HashUtils.deep_flatten_hash applied the prefix to scalar and nested-hash keys, but not to array-valued keys — the String|Symbol, Array branch keyed them by the bare key.to_s:

in String | Symbol, Array
  memo[key.to_s] = deep_flatten_hash(value)            # before — prefix dropped
  memo[prefix ? "#{prefix}.#{key}" : key.to_s] = ...   # after  — prefix honoured

So a caller passing a prefix got a mix of namespaced and un-namespaced keys, e.g.:

deep_flatten_hash({ id: 1, tags: [{ k: 'v' }] }, 'span')
# before => { "span.id" => 1, "tags" => [{ "k" => "v" }] }
# after  => { "span.id" => 1, "span.tags" => [{ "k" => "v" }] }

Why

Discovered while adding webhook.* OpenTelemetry span attributes in application_management_system, where the un-prefixed array keys (assignees, documents) escaped the webhook. namespace and had to be re-namespaced with a transform_keys workaround. This makes the helper consistent so that workaround can be dropped once released.

Safety

Callers that pass no prefix are unaffected — with prefix = nil both branches produce key.to_s (every existing caller in the codebase calls it without a prefix).

Tests

Adds deep_flatten_hash coverage (flat, nested, prefixed scalar/hash, prefixed array regression, no-prefix array) and a deep_dup test. CHANGELOG entry under Unreleased.

🤖 Generated with Claude Code