Async ops now support cancel_after and similar tokens

[anarthal]

All initiations have now an associated executor.

close #330

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.69%. Comparing base (a20fc3e) to head (8399774).

Additional details and impacted files

[](https://app.codecov.io/gh/boostorg/mysql/pull/331?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=boostorg) ```diff @@ Coverage Diff @@ ## develop #331 +/- ## =========================================== + Coverage 98.60% 98.69% +0.08% =========================================== Files 140 141 +1 Lines 7108 7115 +7 =========================================== + Hits 7009 7022 +13 + Misses 99 93 -6 ``` | [Files](https://app.codecov.io/gh/boostorg/mysql/pull/331?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=boostorg) | Coverage Δ | | |---|---|---| | [include/boost/mysql/connection\_pool.hpp](https://app.codecov.io/gh/boostorg/mysql/pull/331?src=pr&el=tree&filepath=include%2Fboost%2Fmysql%2Fconnection_pool.hpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=boostorg#diff-aW5jbHVkZS9ib29zdC9teXNxbC9jb25uZWN0aW9uX3Bvb2wuaHBw) | `100.00% <100.00%> (ø)` | | | [include/boost/mysql/detail/async\_helpers.hpp](https://app.codecov.io/gh/boostorg/mysql/pull/331?src=pr&el=tree&filepath=include%2Fboost%2Fmysql%2Fdetail%2Fasync_helpers.hpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=boostorg#diff-aW5jbHVkZS9ib29zdC9teXNxbC9kZXRhaWwvYXN5bmNfaGVscGVycy5ocHA=) | `100.00% <100.00%> (ø)` | | | [include/boost/mysql/detail/connection\_impl.hpp](https://app.codecov.io/gh/boostorg/mysql/pull/331?src=pr&el=tree&filepath=include%2Fboost%2Fmysql%2Fdetail%2Fconnection_impl.hpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=boostorg#diff-aW5jbHVkZS9ib29zdC9teXNxbC9kZXRhaWwvY29ubmVjdGlvbl9pbXBsLmhwcA==) | `95.23% <100.00%> (+4.83%)` | :arrow_up: | ------ [Continue to review full report in Codecov by Sentry](https://app.codecov.io/gh/boostorg/mysql/pull/331?dropdown=coverage&src=pr&el=continue&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=boostorg). > **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=boostorg) > `Δ = absolute (impact)`, `ø = not affected`, `? = missing data` > Powered by [Codecov](https://app.codecov.io/gh/boostorg/mysql/pull/331?dropdown=coverage&src=pr&el=footer&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=boostorg). Last update [a20fc3e...8399774](https://app.codecov.io/gh/boostorg/mysql/pull/331?dropdown=coverage&src=pr&el=lastupdated&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=boostorg). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=boostorg).