Fix range suppresor formatter

[Soumik15630]

Fixes #4123.

Problem

The formatter specialization for container adaptors (like std::stack, std::queue, std::priority_queue) was overly aggressive. It matched any type with a container_type member alias, causing ambiguous partial specializations when someone tried to define a custom formatter for their own types that happened to have a container_type.

Solution

added a fmt::is_container_adaptor<T> trait. This defaults to std::true_type but allows users to specialize it to std::false_type for their custom types. This removes the library's adaptor formatter from the overload set via SFINAE, resolving the ambiguity and allowing custom formatters to work.

Verification

Added a regression test in test/ranges-test.cc (container_adaptor_partial_specialization) to test the fix and all

thanks .. please let me know if anything need to be changed

[Soumik15630]

@vitaut Tried to fix the problem, check once and please let me know if I need to update anything
Thanks ..

[Soumik15630]

Ping!
Friendly ping — this PR has all ci checks passed.
Let me know if there’s anything else needed.
Thanks 👍

[vitaut]

Thanks for the PR! I don't think we should introduce another trait for this. Have you tried applying the suggestion from #4123 (comment)?

[Soumik15630]

Thanks for the PR! I don't think we should introduce another trait for this. Have you tried applying the suggestion from #4123 (comment)?

I considered the approach from #4123, but it would disable formatting for standard adaptors like std::stack, std::queue, and std::priority_queue.
These types are not ranges and resolve to range_format::disabled, so checking != disabled would incorrectly exclude them. The current == disabled logic is what allows the adaptor formatter to trigger correctly.

I introduced the is_container_adaptor trait to distinguish between "standard adaptors (which are disabled ranges)" and "user types that explicit opt-out via is_range specialization."

Let me know if I missed something or if you'd like me to proceed differently!