Add byte data to metadata summary page for its children thumbnails

[wangf1122]

The parent metadata can contain large amounts of children record and on its summary page, it displays their thumbnails.

The issue was it was url for each of the thumbnail which invokes its resource API and with large volumes of HTTP traffic it will crash the application if the backend database pool is relative small.

This pull request will alter the search service to have the data as part of the children in related records.

and these byte data from the search engine can be used to the HTML/Javascript

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[josegar74]

I have tested it and it works as described, but the response with 2 children goes from 40kb (which also seems a bit high to me, maybe the fields returned for the relations should be reduced?) to 80kb.

@fxprunayre can you check the pull request too? I know that some users have series with hundreds of children, so this may improve the number of http requests made, but also substantially increase the size of the related query responses.

[wangf1122]

@josegar74

Another option or maybe extra feature to introduce is to have this more button (it only load four records at one time)

I checked the UI code and this is some Javascript module for footer.html's but wondering if we can add similar to the related.html

[fxprunayre]

I know that some users have series with hundreds of children, so this may improve the number of http requests made, but also substantially increase the size of the related query responses.

One example https://sdi.eea.europa.eu/catalogue/srv/eng/catalog.search#/metadata/3c362237-daa4-45e2-8c16-aaadfb1a003b

[davidblasby]

@fxprunayre - looking at the page you indicated (https://sdi.eea.europa.eu/catalogue/srv/eng/catalog.search#/metadata/3c362237-daa4-45e2-8c16-aaadfb1a003b).

I see about 133 graphic overview requests - totally about 8mb. Total page load time was 5 seconds. The page was mostly visible after a bit more than 1 seconds.

Also, please see -
#8622

Which limits the total number to 4 (probably should be more than 4).

[ianwallen]

I vote for 20 with a more button that would load the next 20.
20 is little more than a page full and it is a multiple of 4.

At 133, it would only require 6 clicks on the more button.
There could probably be an option to "all" so it can be in one click.

In the future it could be a config value if needed.

[josegar74]

This change, with the limit to display initially 20 related records from #8622 looks fine to me.