Add settings for meta image thumbnail

[protoroto]

Description

Add settings for meta image thumbnail. Commit for setting taken from @adrien-delhorme , refactor setting to be None by default. Also image_width and image_height should take that setting in consideration. Added a test.

References

Fix #718

Fix #717

Checklist

• [x] I have read the contribution guide
• [x] Code lint checked via inv lint
• [x] changes file included (see docs)
• [ ] Usage documentation added in case of new features
• [x] Tests added

[coveralls]

coverage: 97.115% (+0.02%) from 97.094% when pulling 69ca9c9fc27a0786d033132633ad460752525b9f on protoroto:feature/issue-718-add-settings-for-meta-image-thumbnail into 028f01edfa62841ee1eb5d4380cfee701252be8a on nephila:develop.

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.04 :tada:

Comparison is base (028f01e) 94.24% compared to head (69ca9c9) 94.28%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #743 +/- ## =========================================== + Coverage 94.24% 94.28% +0.04% =========================================== Files 26 26 Lines 1824 1837 +13 Branches 260 263 +3 =========================================== + Hits 1719 1732 +13 Misses 53 53 Partials 52 52 ``` | Flag | Coverage Δ | | |---|---|---| | unittests | `94.28% <100.00%> (+0.04%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=nephila#carryforward-flags-in-the-pull-request-comment) to find out more. | [Impacted Files](https://app.codecov.io/gh/nephila/djangocms-blog/pull/743?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=nephila) | Coverage Δ | | |---|---|---| | [djangocms\_blog/models.py](https://app.codecov.io/gh/nephila/djangocms-blog/pull/743?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=nephila#diff-ZGphbmdvY21zX2Jsb2cvbW9kZWxzLnB5) | `98.08% <100.00%> (+0.06%)` | :arrow_up: | | [djangocms\_blog/settings.py](https://app.codecov.io/gh/nephila/djangocms-blog/pull/743?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=nephila#diff-ZGphbmdvY21zX2Jsb2cvc2V0dGluZ3MucHk=) | `100.00% <100.00%> (ø)` | |

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.