Support suffix of id attribute in element of svg

[ChanTsune]

Thanks for the wonderful library!

I wanted to use multiple SVG images inline in HTML.

But, currently generated SVG element id attribute is always "smooth" and "round".

Using multiple SVG images inline in HTML causes display issues due to duplicate id attributes.

So I made it possible to add a suffix to the id attribute.

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[ChanTsune]

@googlebot I signed it!

[brianquinlan]

Very nice change, thanks!

[brianquinlan]

How about Optional[str] = None and then we have some code like:

if id_suffix is None:
  id_suffix = str(uuid.uuid4())

?

What do you think? That would mean that the tests need to be updated and the major version of the library bumped?

Or do you think that it is better to leave the default?

[ChanTsune]

Thank you for your review!

I think adding a random string seems like a good suggestion.

However, the W3C state that:

they cannot start with a digit, two hyphens, or a hyphen followed by a digit.

https://www.w3.org/TR/CSS21/syndata.html#characters.

When using str(uuid.uuid4()), there are cases where a number exists after -.

>>> str(uuid4())
'e489d2a0-39c3-4508-94c5-8337581da1a3'

So I think it's better to remove the - or leave it as it is.

Also, if keep the current PR, you don't have to update the major version, which is a merit I think.