I would design the interface like this:
\defineauthor[john][name={John Doe}, email={john.doe@gmail.com}, affiliation={....}]
\defineauthor[jill][name=..., email=..., affiliation=...]
\setupdocument
[title={....},
authors={john, jill}]
\startdocument
....
\stopdocument
Note that ConTeXt already defines a \setupdocument and \startdocument ... \stopdocument command that are meant to handle document metadata. \startdocument calls \starttext and \stopdocument calls \stoptext, so you do not need to explicitly add them (although adding them does no harm). In order for the above setup to work you need to define:
\startsetups document:start
\documentvariable{title} % Use this to get the document title
\documentvariable{author} % Use this to get the list of authors
\stopsetups
\startsetups document:stop
% If you want to place something at the end of a document
\stopsetups
So, all that is left is to define the \defineauthor command. If you are using MkIV, you may simply use:
\definenamespace
[documentauthor] % name of internal varialbles
[type=module,
name=author,
command=yes, % Create \defineauthor
style=yes, % Create \useauthorstyleandcolor
setup=list, % Create \setupauthor
parent=documentauthor,
]
which will create the required command.
The above may appear like an overkill for adding authors, but it does provide you will the following features:
Inherit keys across authors. Suppose you have multiple authors at the same institute, and you don't want to pass on the affiliation each time. Then you can do:
\defineauthor[univ1][afficiation={TeX University}]
\defineauthor[john][univ1][name=..., email=...]
\defineauthor[jill][univ1][name=..., email=...]
and both john and jill will inherit the affiliation from univ1.
Create an author database: You can create an author database in a separate file and use
\environment author-database
in all your files. This way, you only define the authors once and can use them in all your documents.
EDIT: Here is a complete example:
\definenamespace
[documentauthor] % name of internal varialbles
[type=module,
name=author,
command=yes, % Create \defineauthor
style=yes, % Create \useauthorstyleandcolor
setup=list, % Create \setupauthor
parent=documentauthor,
]
\define[1]\useauthor
{\edef\currentauthor{#1}%
{\useauthorstyleandcolor{style}{color}
\authorparameter{name}}%
\space
(\mono{\authorparameter{email}})}
\startsetups document:start
\startalignment[middle]
{\ssbfc\setupinterlinespace
\documentvariable{title}
\endgraf}
\blank[medium]
\processcommacommand[\documentvariable{author}]\useauthor
\blank[big]
\stopalignment
\stopsetups
\startsetups document:stop
% If you want to place something at the end of a document
\stopsetups
\setupauthor[style=sansbold]
\defineauthor[john][name={John Doe}, email={john.doe@gmail.com}]
\defineauthor[jill][name={Jill Doe}, email={jill.doe@gmail.com}]
\setupdocument[title={Random title}, author={john,jill}]
\startdocument
\input knuth
\stopdocument
