Solr: add docstrings to the admin app

[WalterMoar]

Task (Use for Work not Directly related to a Story but supports the Sprint Goals)

Detailed Description

The Solr admin app is documented, but not in the pythonic manner described in PEP 257 (Docstring Conventions). Apply the conventions to the application's code so that it is more easily understandable for python developers.

Sprint Goal

Acceptance Criteria

Definition of Done (:one:-Mandatory to add to the Backlog, :two:-Mandatory to add to the Sprint Backlog)

• Acceptance Criteria Defined 1️⃣
• Estimate 2️⃣
• Priority Label 1️⃣
• Task Label 1️⃣
• Assignee 2️⃣
• Sprint Goal (in line with the goal of the sprint) 2️⃣

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