## Issue being fixed or feature implemented
Platform (in the scope of Withdrawals) need to be aware if a tx isn't in
mempool when requesting status of a tx using RPC `gettxchainlocks`.
cc @markin-io
## What was done?
- mempool is passed to `GetTransaction` and saving the result for
checking latter.
- If the returned tx_ref is nullptr, then the RPC returns null for the
corresponding tx in the array.
Example:
`tx1` is mined and chainlocked, `tx2` is in mempool and `tx3` doesn't
exist.
The result now is:
`[
{
"height": 830,
"chainlock": false,
"mempool": true
},
{
"height": -1,
"chainlock": false,
"mempool": true
},
{
"height": -1,
"chainlock": false,
"mempool": false
}
]`
## How Has This Been Tested?
## Breaking Changes
## Checklist:
- [x] I have performed a self-review of my own code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have added or updated relevant unit/integration/functional/e2e
tests
- [ ] I have made corresponding changes to the documentation
- [x] I have assigned this pull request to a milestone _(for repository
code-owners and collaborators only)_
---------
Co-authored-by: Konstantin Akimov <knstqq@gmail.com>
Co-authored-by: UdjinM6 <UdjinM6@users.noreply.github.com>
