Add a Docstring for all functions in the code and the tests

[Justus Ortlepp]

As an Tazama Platform Implementer,
I want every function in the platform described with a docstring,
So that I can understand what the function does without reading the documentation somewhere else

Acceptance Criteria

1. Cover every custom function in every module of code and test with a docstring.

  /**
   * @param collection Collection name against which this query will be run
   * @param filter String that will put next to the FILTER keyword to run against Arango
   *
   * ```
   * const query = aql`
   * FOR doc IN ${collection}
   * FILTER ${filter}
   * RETURN doc`;
   * ```
   *
   * Note, use "doc." in your query string, as we make use of "doc" as the query and return name.
   * @memberof PseudonymsDB
   */
  queryPseudonymDB: (collection: string, filter: string, limit?: number) => Promise<any>;

2. Find a way to progressively roll out docstrings to every function

Acceptance criteria

1. Update the definition of done
2. Update the contribution guide
3. Fix as we go

[Justus Ortlepp]

Added to https://github.com/frmscoe/docs/blob/dev/Community/Tazama-Contribution-Guide.md 5.2.1