LMS-154 Include images in individual amendments accessed from api

Summary of feature request

Include images in individual amendments when accessed from the individual amendment api on the PDR.

Further background

Images can be included in amendments in the same way they can be included in Bills and SIs etc, although it is a very rare occurrence.

Currently, if you access the zip file of an amendment list via the api it will include any images included in the amendments as separate files. However, only the xml of amendments is available when you download an individual amendment.

Original description of issue - E-mail from Tom Kelly, 24 May 2022

I suspect we’re going to need to request an adjust the above. There are a few options that immediately jump out to me

1. Base64 encode the image into the XML doc img element

2. Describe in the XML doc where on the API the image can be retrieved from

 It feels like option 1 might be worth considering, as then the XML document contains all the information relating to the amendment without any other files having to also be downloaded.

 Can you take a look at this and let me know what you think?