add mapping.toml support

[miDeb]

Supports specifying:

• a unique name for fields
• a slope + offset conversion for a "mapped value"
• a range-based conversion for a "logical value", that also includes a color code for the frontend

NodeManager now supports reading raw, mapped, and logical values by mapping name, requesting mapped fields from nodes, and writing mapped parameter values back as raw CAN values.

I also added some validation rules for the mapping.

Depends on #14 because I read the path to the mapping from the config.

Please take a look at tests/mapping/example1.toml to see how a mapping file would look like. There are two ways to specify a mapping in there, which are only syntactically different, as toml has multiple ways to specify nested tables (=objects in json). The second example uses inline tables to a greater extent, and of course there are even more syntactically correct ways to write the same thing in toml.

I'll open this as a draft until we agree on the format of the mapping.

[raffael0]

Hi,
I added quite a few tests. Just as a disclaimer: The second commit was pretty vibe coded. I looked over the tests though and they look fine to me.

Also I noticed that the only way right now to request a new value is through the request_value method, which requires the mapped name. This means that there is no way right now to request a value without a mapping. I think it would make more sense for request_value to first look if the name is a raw value(and then request that) and only if that fails then look at the mapped names.

As a consequence values could be accessed via mapped/raw names interchangeably. This behaviour would make more sense to me. What do you think?

[miDeb]

In #21 I cleaned this up a bit by adding request_field_by_mapped and request_field_by_raw, but I guess it could also make sense to have one function that checks first for a potential mapping, and if that does not exist, uses the name as a raw name. However it would have to take the node name (or id) as well because raw names are not necessarily unique across all nodes.