Update Dockerfile

[ajkyffin]

Merges main into this branch. Only the last commit needs to be reviewed.

• Split into a build stage and an install/run stage
• Use the python:3-alpine base image
• Run as a non-root user
• Add an entrypoint script that sets values in config.yaml from environment variables

[codecov]

Codecov Report

Base: 94.47% // Head: 42.30% // Decreases project coverage by -52.18% ⚠️

Coverage data is based on head (e7630dc) compared to base (6c7332e).
Patch coverage: 98.22% of modified lines in pull request are covered.

Additional details and impacted files

@@                 Coverage Diff                 @@
##           k8s-deployment     #402       +/-   ##
===================================================
- Coverage           94.47%   42.30%   -52.18%     
===================================================
  Files                  39       39               
  Lines                3114     3319      +205     
  Branches              311      310        -1     
===================================================
- Hits                 2942     1404     -1538     
- Misses                144     1907     +1763     
+ Partials               28        8       -20     

Impacted Files	Coverage Δ
datagateway_api/src/datagateway_api/backends.py	0.00% <ø> (-100.00%)	⬇️
...ateway_api/src/datagateway_api/database/helpers.py	0.00% <0.00%> (-77.22%)	⬇️
...atagateway_api/src/datagateway_api/icat/helpers.py	0.00% <0.00%> (-94.58%)	⬇️
...ay_api/src/datagateway_api/query_filter_factory.py	30.30% <ø> (-69.70%)	⬇️
...api/src/resources/entities/entity_endpoint_dict.py	100.00% <ø> (ø)
datagateway_api/src/search_api/filters.py	0.00% <0.00%> (-98.91%)	⬇️
datagateway_api/src/common/config.py	98.68% <100.00%> (-1.32%)	⬇️
...gateway_api/src/datagateway_api/database/models.py	94.32% <100.00%> (-2.13%)	⬇️
datagateway_api/src/search_api/models.py	99.52% <100.00%> (+<0.01%)	⬆️
datagateway_api/src/common/constants.py	0.00% <0.00%> (-100.00%)	⬇️
... and 32 more

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[VKTB]

Best to pin the version of Python to prevent unexpected breakages in future.

[ajkyffin]

Resolved in dfb54ba