This PR was merged into the 3.0-dev branch.

Discussion
----------

[3.0] Added getBlockPrefix to FormTypeInterface

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | yes
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Commits
-------

d834cd3 Added getBlockPrefix to FormTypeInterface

…ce (webmozart)

This PR was merged into the 3.0-dev branch.

Discussion
----------

[Form] Added getBlockPrefix() to ResolvedFormTypeInterface

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

This is the follow-up PR to #16724.

If you call `$form->getConfig()->getType()`, all the methods of FormType should be usable. In that sense, ResolvedFormType is the developer-facing version of FormType.

It is true that the same could be achieved with `getInnerType()`, but that method should be used in edge cases only as it clutters the code and makes it confusing to read:

```php
$blockPrefix = $form->getConfig()->getType()->getInnerType()->getBlockPrefix();
```

Commits
-------

7e89345 [Form] Added getBlockPrefix() to ResolvedFormTypeInterface

This PR was submitted for the master branch but it was merged into the 3.0 branch instead (closes #16752).

Discussion
----------

[Form] document changes to form type interfaces

| Q             | A
| ------------- | ---
| Fixed tickets | #13407, #16024, #16724, #16749
| License       | MIT

Commits
-------

b297a0c [Form] document changes to form type interfaces