cdm-lens needs to provide a data policy and usage file for each request

[agstephens]

1. Take response DataFrame, get the source_ids (before we remove from the DataFrame).

2. Take each unique source_id and extract the following fields from the source_configuration table, e.g.:

SELECT product_name, product_references, product_citation FROM source_configuration WHERE source_id = 166;

3. For each observation_id, take the first two characters as the country code.

4. Look up the "Data Policy Link" from the country code.

5. Compile that unique set into a text file and save it as part of the output zip file. Each item might include:

   • data policy link
   • product_name (i.e. the source name)
   • product_references
   • product_citation

[agstephens]

Format:

For each source:

Source: <source_id> - <product_name>
Product references:
....
Product citations:
...

Then, for each country code:

National Data Policy Information: (<abbrev>) - <country>
<link>

[agstephens]

Initial implementation is here:

https://github.com/glamod/cdm-lens/blob/master/cdm_interface/data_policies.py

Still requires:

1. Loaded full.source_configuration table, or local version available as a file.
2. Connection to the views.py and should be written to an output file.

[agstephens]

Linked to #21 and #39

[agstephens]

Implemented in commit: https://github.com/glamod/cdm-lens/commit/8b82e84528d1a086784ae92ce8c01b3c81bafa8d