v1: uri (CXX-3237, CXX-3238)

[eramongodb]

Resolves CXX-3237 and CXX-3238 for the v1::uri component.

To continue to support implicit conversion from e.g. char const* -> string::view_or_value without ambiguity with the v1 ctor (because v1::uri also has a non-explicit string_view ctor), a constrained non-explicit constructor template is added to have higher priority for convertible-to-string::view_or_value arguments than the non-explicit v1 ctor.

This PR also adds /Zc:strictStrings (part of /permissive-, which we do not yet enable) to avoid non-conforming behavior with MSVC which interacts poorly with our void* ctor (even when private or explicit). This flag is applied to mongocxx library (and test) builds only and is not inherited by users. We can consider adding a char const* ctor instead, but I'd prefer depending on and encouraging standard conformance instead.

Additional notes:

• Fix missing const qualifiers for getters overlooked by CXX-3236 add mongocxx v1 declarations #1482.
• Try to use new mongoc URI API when able.
• Try to use v1 bsoncxx API instead of bson when able; however, cannot use bsoncxx for URI field lookup due to backward compatibility with case (in)sensitivity lookups. Not all options may support canonicalization into lowercase form.
• v_noabi::uri remains non-copyable for backward compatibility despite v1::uri being copyable.

[kevinAlbs]

LGTM with minor comments.

[kevinAlbs]

Minor: also test C function returning NULL causes C++ member function to return unset optional:

template <typename MemFn, typename Mock>
void test_string_opt(MemFn mem_fn, Mock& mock) {
    uri const opts;
    auto const identity = uri::internal::as_mongoc(opts);

    auto const v = GENERATE(bsoncxx::v1::stdx::optional<char const>{}, bsoncxx::v1::stdx::optional<char const>{'\0'});

    auto fn = mock.create_instance();
    fn->interpose([&](mongoc_uri_t const* ptr) -> char const* {
        CHECK(ptr == identity);
        if (v.has_value()) {
            return &(*v);
        }
        return nullptr;
    });

    auto const opt = (opts.*mem_fn)();
    if (v.has_value()) {
        REQUIRE(opt.has_value());
        CHECK(opt->data() == static_cast<void const*>(&(*v)));
    } else {
        CHECK(!opt.has_value());
    }
}

[kevinAlbs]

Minor: also test C function returning NULL causes C++ member function to return unset optional:

template <typename MemFn, typename Mock>
void test_doc_opt(MemFn mem_fn, Mock& mock) {
    uri const opts;
    auto const identity = uri::internal::as_mongoc(opts);

    auto const v =
        GENERATE(bsoncxx::v1::stdx::optional<scoped_bson>{}, bsoncxx::v1::stdx::optional<scoped_bson>{R"({"x": 1})"});

    auto fn = mock.create_instance();
    fn->interpose([&](mongoc_uri_t const* ptr) -> bson_t const* {
        CHECK(ptr == identity);
        if (v.has_value()) {
            return v->bson();
        }
        return nullptr;
    });

    auto const opt = (opts.*mem_fn)();
    if (v.has_value()) {
        REQUIRE(opt.has_value());
        CHECK(opt->data() == v->view().data());
    } else {
        CHECK(!opt.has_value());
    }
}

[kevinAlbs]

Suggested change

	TEST_CASE("exceptions", "[bsoncxx][v1][uri]") {
	TEST_CASE("exceptions", "[mongocxx][v1][uri]") {

[kevinAlbs]

Remove duplicate check.

Suggested change

CHECK_FALSE(opts.server_selection_try_once().has_value());

[kevinAlbs]

Remove non-applicable docs.

Suggested change

	/// @par Postconditions:
	/// - `other` is in an assign-or-destroy-only state.
	///
	/// @warning Invalidates all associated iterators and views.

[kevinAlbs]

Remove unnecessary template? I expect it is not needed since there is only one specialization.

Suggested change

	template <typename T>
	bsoncxx::v1::stdx::optional<T> get_credentials_field(mongoc_uri_t const* uri, char const* field);
	template <>
	bsoncxx::v1::stdx::optional<bsoncxx::v1::document::view> get_credentials_field(
	bsoncxx::v1::stdx::optional<bsoncxx::v1::document::view> get_credentials_field(