Contentful: custom content model

[AlbertGom]

Description

Create custom content

Context

There was no custom content model where you can add custom fields without having to be defined in the plugin.

Approach taken / Explain the design

Created a new component that has id,name and fields. Fields field is a record that has the custom fields defined in contentful.

To document / Usage example

Testing

The pull request...

• has unit tests

[asastre]

Although I have approved the PR @AlbertGom take a look at the tests, they're failing!

[github-actions]

Unit Test Results

  1 files  ±0    7 suites  ±0   2m 34s ⏱️ -33s
32 tests ±0  32 ✔️ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 3b9d07d. ± Comparison against base commit 1a09393.

♻️ This comment has been updated with latest results.

[asastre]

The changes done before the last commit allowed to fetch custom content from Contentful only if the content model was named 'custom'.
With the changes done in the last commit allow fetching all type of content models different than the known ones (text, image, button, etc.).
@AlbertGom can you review this last commit?

[AinaVendrell]

🚀