Add internal presets for charging station output

[tomasmarklund]

For preset amenity=charging_station, there are a number of presets for different sockets.

For each of the different sockets, there should also be an output tag:

socket:<type>:output=*

See wiki: ​https://wiki.openstreetmap.org/wiki/Key:socket

Example: for all the (as today) 7793 objects with socket:type2_combo, 5881 of them also have the tag socket:type2_combo:output

​https://taginfo.openstreetmap.org/keys/socket%3Atype2_combo#combinations

[taylor.smock]

I get where you are coming from, but I don't think our preset system can currently handle the explosion of tags this would generate, especially from the UI side. We would (effectively) be doubling the size of the window for sockets if we just did the socket:<type>:output addition.

We would want to have a preset element for something like this, e.g.

<metatags>
    <metatag ref="type" key="type1" text="SAE J1772 (IEC Type 1)"/>
    <metatag ref="type" key="type1_combo" text="SAE J1772 Combo (DC)"/>
    <combo key="socket:{type}" values="1,2,3,4,5,6" text="Count of socket types, or yes if unknown"/>
    <combo key="socket:{type}:current" values="16,32" text="Current in amperes"/>
    <combo key="socket:{type}:voltage" values="230,400" text="Voltage in volts without unit and thousand delimiters"/>
    <text key="socket:{type}:output" text="Output of any single socket in kW"/>
</metatags>

An example using parking lanes to show why the ref attribute would be useful

<metatags>
    <metatag ref="direction" key="right" text="Right of way direction"/>
    <metatag ref="direction" key="left" text="Left of way direction"/>
    <metatag ref="type" key="parallel" text="Parallel parking"/>
    <metatag ref="type" key="diagonal" text="Diagonal parking"/>
    <combo key="parking:lane:{direction}:{type}" values="on_kerb,on_street"/>
</metatags>

We may already have something like that, but I don't know what it is.

UI wise, each composed tag would be an option in a dropdown list, which then adds additional fields for the user to fill in.