Add new custom_values field

[yg0x01]

According to the documentation, add compatible custom values content from the latest version.

[LukaOber]

Is there a reason I am missing for using

#[serde(skip_serializing_if = "Option::is_none")]
custom_values: Option<Vec<CompositeValue>>,

instead of

#[serde(skip_serializing_if = "Vec::is_empty")]
custom_values: Vec<CompositeValue>,

[yg0x01]

Sorry, I didn't think it through carefully and just followed the examples around. Using skip_serializing_if = "Vec::is_empty" for the Vec<_> type instead of Option<Vec<_>> is simpler. I have corrected it.

[LukaOber]

Is the push syntax the better choice here? You implemented this.

pub fn custom_values<C: Into<CompositeValue>>(mut self, custom_value: C) -> Self {
    self.custom_values.push(custom_value.into());
    self
}

But do we actually want to push several times, or would the following be the better approach? I think the latter would be better for setting custom values. What do you think? How are you going to use it?

pub fn custom_values<C: Into<CompositeValue>>(mut self, custom_value: C) -> Self {
    self.custom_values = custom_values.into_iter().map(|c| c.into()).collect();
    self
}

[yg0x01]

I wish I could directly set this array without needing to loop and use push. However, after looking at how vectors are handled in other places, I noticed that many use push. I think it would be better to provide both methods for vectors: one for push and another for directly setting the array. However, this could be a lot of work. For this case, I prefer the direct setting approach. I have modified the code based on your suggestion.

[LukaOber]

Sorry for all the hassle, thank you for opening and implementing my suggestions.