refactor(ui): support custom file display name resolver

[zubeydecivelek]

closes CERNDocumentServer/cds-rdm#652

❤️ Thank you for your contribution!

Description

• This change allows the file names shown on the record page to be customized by passing a small resolver function to the file UI macros.

• Instead of always displaying the file key, instances can customize how the file name should be derived (for example: using file.metadata.title instead of file.key).

• New block added to make customization of the file name, without overriding the record_files block.

Checklist

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Frontend

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[zzacharo]

Suggested change

	{%- set display_name = resolve_display_name(file) or file.key %}
	{%- set human_readable_file_name = display_name(file) or file.key %}

[zzacharo]

Suggested change

	{{ file_list_box(files, record_ui["id"], is_preview, include_deleted, record, permissions) }}
	{%- block record_files_container -%}
	{{ file_list_box(files, record_ui["id"], is_preview, include_deleted, record, permissions) }}
	{%- endblock record_files_container -%}