[Reopen] Add API for checking the task is existing without throwing error

[amokio]

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PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[slavik-pastushenko]

Hi :)
What about using enum for type? Maybe it will be easier to support it.
Cause if someone will add new type, or rename existing, it'll be additional work to change in all files instead of one string in enum?

[amokio]

I think here is unnecessary to use enum. Since the type of the task/job is already limited. There may only have interval, timeout, and cronjob.

Anyway, thanks for the code review. If the creator really want to use enum, I will update it and push it again

[kamilmysliwiec]

LGTM thanks!