feat(flagd): add support for azure blob

[VMaievskyi]

This PR

Allow to configure Azure Blob as source for config
Verified that Flagd sidecar is created and connected to Azure Blob (SAS Key used for access)

Related Issues

Relates to:
#765
#758

Notes

At current moment it can work only with FeatureFlagSource.envVarPrefix = "" and spec.sidecarConfiguration: ""
as prefix breaks env var name and flagd cannot find mandatory env variables.

Follow-up Tasks

Fix flagd to search for Azure blob env vars ignoring prefix.

How to test

Works with end-to-end.yaml

apiVersion: core.openfeature.dev/v1beta1
kind: FeatureFlagSource
metadata:
  name: end-to-end
  namespace: open-feature-demo
spec:
  sources:
  - source: azblob://my-bucket/test.json
    provider: azblob
  envVarPrefix: ""
  envVars:
  - name: AZURE_STORAGE_ACCOUNT
    value: <account_name>
  - name: AZURE_STORAGE_SAS_TOKEN
    value: <SAS token>

[codecov]

Codecov Report

❌ Patch coverage is 60.00000% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.25%. Comparing base (499661e) to head (7ee876d).
⚠️ Report is 71 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/common/flagdinjector/flagdinjector.go	0.00%	8 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #779       +/-   ##
===========================================
- Coverage   86.51%   71.25%   -15.26%     
===========================================
  Files          19       30       +11     
  Lines        1587     2324      +737     
===========================================
+ Hits         1373     1656      +283     
- Misses        173      620      +447     
- Partials       41       48        +7     

Files with missing lines	Coverage Δ
api/core/v1beta1/common/common.go	84.90% <100.00%> (ø)
api/core/v1beta1/featureflagsource_types.go	96.90% <100.00%> (ø)
internal/common/flagdinjector/flagdinjector.go	88.29% <0.00%> (ø)

... and 11 files with indirect coverage changes

Flag	Coverage Δ
unit-tests	71.25% <60.00%> (∅)

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[VMaievskyi]

@beeme1mr could you please have a look?

[beeme1mr]

Thanks for the PR and sorry for the delayed approval. I had some feedback on the env changes but everything else looks good.

[lukas-reining]

Looks good to me! Thanks @VMaievskyi!