Add possibility to change function passed to handleSubmit

[ideffix]

Closes #4682

When submiting form remotely by dispatching submit action and during Form lifetime and method provided to handleSubmit has changed - it isn't fired - only first function provided to Form is fired. After invastigation I've noticed that for remote submitting submit function from createReduxForm.js calls method innerOnSubmit() and it is set with following function: registerInnerOnSubmit: innerOnSubmit => (this.innerOnSubmit = innerOnSubmit).
In Form.js I can see that it only register method when component will mount this.props._reduxForm.registerInnerOnSubmit(this.props.onSubmit) so even if you change method provided to handleSubmit during Form life, it wont be fired onSubmit.
My fix adds possibility to change that method during Form life.

[ideffix]

Hi @iamandrewluca, can we do something with it?

[iamandrewluca]

We don't want to add any legacy things, this will make development of library even harder if we want to move on with next versions of react.

Note:

These methods are considered legacy and you should avoid them in new code:

UNSAFE_componentWillUpdate()
UNSAFE_componentWillReceiveProps()
— https://reactjs.org/docs/react-component.html

[ideffix]

@iamandrewluca I've changed unsafe methods of this component

[iamandrewluca]

Thankss @ideffix, I'll find some time to make a new release.

[ideffix]

Hi @iamandrewluca, I know its been a while since this PR was merged to master, but can we have a realease version with it? I kinda need it now :D

[erikras]

Published in v8.3.7.

[iamandrewluca]

@ideffix FYI

[ideffix]

Gr8, thanks guys! 🥇