Header: Allow to use a string list, for frontmatter key. Use the {{syntax}} to recognize key

[Mara-Li]

feat(header): use a list for banner_header, allowing to use frontmatter keys

Support list and string.

• For list: Use the first key found in the list. Otherwise, join the list with a space.
• For string, replace the {{key}}, allowing to combine keys and simple value.

Key supported:

• {{file}} : Use basename
• {{anykey}} : use this key if exists. If the key is an array, use the first.

[!NOTE] For alias, automatically convert to aliases because Obsidian convert automatically this key if it's a string.

Also added new settings:

• Use the filename as default
• Set a property key

See #125

[Mara-Li]

If anyone is interested, you can try my PR using the release ! https://github.com/Lisandra-dev/obsidian-banners/releases/tag/2.0.2-beta

[noatpad]

Pardon the delay, had an exam week, ahah.

So I moved around a few things, but in a nutshell:

• I moved the logic to transformers.ts since in hindsight, it makes sense to keep that logic together there at the level where the YAML is turned into relevant banner data.
• Because of possible incompatibilities for future Obsidian releases (https://github.com/noatpad/obsidian-banners/issues/121), the header property can't be of different types, so it has to remain a text/string property. As a compromise, I implemented the ability to add multiple fields within the curly braces that can act as fallbacks (so something like {{author, title, filename}}). It's a bit more flexible this way as a result too.
• Reworded a few settings for clarity
• Empty/null values work differently though. Empty text properties (ie null values) are now treated as empty in favor of {{filename}}. This is because it can act as an override to the "Display header by default" setting

Do tell if this may still present issues!

[Mara-Li]

Hello! Thanks for the reply <3 you have better idea than me!

I added just a little information in the settings about the {{property, property2, filename}} fallback syntax!