docs: Update io.cozy.accounts doc

[LucsT]

Update of the object io.cozy.accounts according to our meeting.

Remove old never use attributs, label, folderPath Use of defaultFolderPath. Clarify login fields as existing now Introduce role: 'identifier' marker.

[LucsT]

I made a second pass. Enhance form and formatting too. I enhance the example with a real world example. I add some mention of the identifier field that would maybe be deprecated. We probably need a meeting to clarify this point identifier field, marker role:identifier. What do we really want, and what we document here.

I didn't expect @Crash-- and @sblaisot to be added in review as soon. But your advice are welcome.

[LucsT]

@doubleface @taratatach I updated the docs with the elements from our meeting. What do you think about it now ?

[LucsT]

I just removed the double 'n' from Optional

[LucsT]

@taratatach Great addition. I marked identifier as optional because of banking account do not use it. I commited your proposals and squash it into a nice commit.

Good to merge for you ?

[taratatach]

@LucsT if identifier is optional, it would be nice to modify the section about the account name to reflect this :slightly_frowning_face: . How is the name of a banking konnector account determined?

[LucsT]

@taratatach I fix a typo, Change a Once in a If, about the optional identifier field And add a comment about banking konnectors, but they respect the rules with a identifier:'identifier'. A little weird but ok.

Are you okay ? Don't look at the commit name, i will squash it after you read it.