function m2mName(declarationModelName, fieldName) {
    return declarationModelName + capitalize(fieldName);
}
Returns the branch name for a many-to-many relation.
The name is the combination of the model name and the field name the relation
was declared. The field name's first letter is capitalized.

Example: model `Author` has a many-to-many relation to the model `Book`, defined
in the `Author` field `books`. The many-to-many branch name will be `AuthorBooks`.

@param  {string} declarationModelName - the name of the model the many-to-many relation was declared on
@param  {string} fieldName            - the field name where the many-to-many relation was declared on
@return {string} The branch name for the many-to-many relation.