translation of field_config is broken

This is a first step, I am adding test to expose the problem and I am trying to not change too much the code in order to avoid mayor changes.

The problem basically is that the configMapper is trying to get a definition of a 'field_config' that doesn't exist so instead of using the type of the job item we should use the type of the $config_mapper, it is the same with other entities but for field_config changes to the good one.

For the UI in the translation of tmgmt, as suggested by @berdir, I am adding a new option 'Field' that has every 'field_config' of entities and then can be translated.

But now the problem is that the translation is not saved, the same as #2566353: Translation is not saved from Account settings so probably we have to fix that in the other issue.

It is related to the core, that function was added recently here #2550945: Add Html::escape() and SafeMarkup::checkPlain was removed so we changed that in #2555045: SafeMarkup::checkPlain is being removed.

Unsure how qualified my response is here. I'm just trying to understand what we do...

1. +++ b/sources/tmgmt_config/src/ConfigSourcePluginUi.php
   @@ -139,7 +139,7 @@ class ConfigSourcePluginUi extends SourcePluginUiBase {
   +      'title' => $entity->getEntityTypeId() == 'field_config' ? $label : $entity->link($label),
   

   This check still seems a bit odd to me. And thus at least need a comment why field_config have no link... EntityInterface guarantees that we can call link() on all entities. So we should fix this bug elsewhere. Otherwise it's not an entity at all?

2. +++ b/sources/tmgmt_config/src/ConfigSourcePluginUi.php
   @@ -308,6 +307,9 @@ class ConfigSourcePluginUi extends SourcePluginUiBase {
   +      if ($type == 'field_config') {
   +        $type = $entities[reset($entity_ids)]->get('entity_type') . '_fields';
   

   Needs a comment about the problem.

3. +++ b/sources/tmgmt_config/src/Plugin/tmgmt/Source/ConfigSource.php
   @@ -287,9 +287,9 @@ class ConfigSource extends SourcePluginBase implements ContainerFactoryPluginInt
   -    foreach ($entity_types as $entity_type_name => $entity_type) {
   ...
   +    foreach ($definitions as $definition_name => $definition) {
   

   Why is this change needed? I would expect that enumerating the entity types is more what we want than enumerating the mappings... (duplicates?)

1. As far as I understand the problem here is that the entity is 'FieldConfig' and it have a link but we want to list the fields of 'fieldable' entities so this ones don't have a link and there are not entities. Added a comment.

2. Commented.

3. It was suggested by @berdir, there are duplicates for field_config but it was the only way to have 'Field' listed on the UI. Another option could be added this manually (?).

Tested locally, everything seems to work just fine.

1. +++ b/sources/tmgmt_config/src/ConfigSourcePluginUi.php
   @@ -139,7 +139,9 @@ class ConfigSourcePluginUi extends SourcePluginUiBase {
          'id' => $entity->id(),
   -      'title' => $entity->link($label),
   +      // If the entity type is FieldConfig, we list the field of the fieldable
   +      // entity type which doesn't have a link.
   +      'title' => $entity->getEntityTypeId() == 'field_config' ? $label : $entity->link($label),
   

   There is a better way to check this, the existence of a edit-form link template.

2. +++ b/sources/tmgmt_config/src/ConfigSourcePluginUi.php
   @@ -308,6 +309,11 @@ class ConfigSourcePluginUi extends SourcePluginUiBase {
   +      if ($type == 'field_config') {
   +        $type = $entities[reset($entity_ids)]->get('entity_type') . '_fields';
   +      }
   

   You have $entity available here, why so complicated?

3. +++ b/sources/tmgmt_config/src/Tests/ConfigSourceListTest.php
   @@ -330,4 +330,17 @@ class ConfigSourceListTest extends EntityTestBase {
    
   +  function testFieldConfigList() {
   

   Missing docblock.

4. +++ b/sources/tmgmt_config/src/Tests/ConfigSourceListTest.php
   @@ -330,4 +330,17 @@ class ConfigSourceListTest extends EntityTestBase {
   +    $this->assertText(t('One job needs to be checked out.'));
   +    $this->drupalPostForm(NULL, array(), t('Submit to translator'));
   +
   +    // Make sure that we're back on the originally defined destination URL.
   +    $this->assertUrl('admin/tmgmt/sources/config/field_config');
   +
   

   We're not really asserting much here. Shouldn't we check that the translation was saved correctly?

5. +++ b/sources/tmgmt_config/src/Tests/ConfigSourceUiTest.php
   @@ -252,6 +252,28 @@ class ConfigSourceUiTest extends EntityTestBase {
   +
   +    // Verify that the pending translation is shown.
   +    $this->clickLink(t('Needs review'));
   +    $this->drupalPostForm(NULL, array(), t('Save as completed'));
   

   Same. You don't need to check if the field config was translated in both, one of them is enough.

   But this one should at least also have some assertText() for a configuration message. This could end in an exception and you wouldn't notice.

1. Done.
2. I realized that if we want to request more than 1 translation, each one have a different type so this could lead to an error with this approach (?).
I added a new key to the items array to save the type and then this is used to add the job. I don't know if is the best way because the type doesn't change with other entities.
3. Added.
4,5. Added text to assert in one of the test.

It' seems to work correcly, the code it's fine. The test fail are unrelated to this issue.

Committed.