is_trivially_copyable doesn't follow the standard's definition

```cpp
#include
#include

struct foo {
foo(foo const&) = delete; // deleted copy constructor
foo& operator=(foo const&) = default;
};

struct bar {
bar(bar const&) = default;
bar(bar &&) {} // user defined move constructor
auto operator=(bar const&) -> bar& = default;
auto operator=(bar && ) -> bar& { return *this; } // user defined move assignment
};

static_assert(not boost::is_trivially_copyable::value);
static_assert( std ::is_trivially_copyable::value);

static_assert( boost::is_trivially_copyable::value);
static_assert(not std ::is_trivially_copyable::value);
```

https://en.cppreference.com/w/cpp/named_req/TriviallyCopyable
types with deleted constructors/move assignment operators are allowed to be trivially copyable, as long as at least one of them is defined, and all the non deleted ones are trivial.