Merge Link & Image Format when using MergeModel

[BryanValverdeU]

Add functionality to merge the link format. So we can successfully merge the target and source styles on paste if the option to merge style is chosen.

Also fix for images, as some formatting like width was getting lost when pasting with mergeFormat option.

Copy the link in this pen and paste and merge format:
https://codepen.io/Bryanvalverdeu/pen/ExzmOKb

Before

After

[JiuqingSong]

Can we just simply copy the format that we want to copy, but not copy all then delete others?

I feel the format we want to keep is less than the ones we want to remove

[JiuqingSong]

Or, if we need to copy everything other than segment format, you can do like this:

1. add a object to contains all properties of segment:

// An object to provide keys of required properties of segment format, the do NOT use any of its values
const requiredEmptySegmentFormat: Required<ContentModelSegmentFormat> = {
  fontFamily: null!,
  ...
}

2. When copy format, delete format with keys of this object

const format = { ... }
getObjectKeys(requiredEmptySegmentFormat).forEach(key => delete format[key]);

So that if we add some new property to segment format in the future, we can still take care of them here since it will break the build.

[BryanValverdeU]

Or, if we need to copy everything other than segment format, you can do like this:

1. add a object to contains all properties of segment:

// An object to provide keys of required properties of segment format, the do NOT use any of its values
const requiredEmptySegmentFormat: Required<ContentModelSegmentFormat> = {
  fontFamily: null!,
  ...
}

2. When copy format, delete format with keys of this object

const format = { ... }
getObjectKeys(requiredEmptySegmentFormat).forEach(key => delete format[key]);

So that if we add some new property to segment format in the future, we can still take care of them here since it will break the build.

This looks better, I agree. Changing this.

The problem I saw with Copying only what we need is that ContentModelHyperlinkFormat and ContentModelImageFormat contain a lot more properties, so I thought removing the unneeded properties would be better.
And also in case there is a customized process/applier so we dont remove other styles.

[JiuqingSong]

Ok, makes sense