fix(loki): allow global and per tenant sigv4 config

[taharah]

Signed-off-by: Trevor Wood Trevor.G.Wood@gmail.com

What this PR does / why we need it:
Fixes an issue that prevented the sigv4 authentication configuration from being set during the resolution of the per tenant overrides. This fixes the issue by allowing the global value to be properly propagated as well as enables setting the sigv4 authentication on a per tenant basis.

Which issue(s) this PR fixes:
Fixes #6293

Special notes for your reviewer:
N/A

Checklist

• Documentation added
• Tests updated
• Is this an important fix or new feature? Add an entry in the CHANGELOG.md.
• Changes that require user attention or interaction to upgrade are documented in docs/sources/upgrading/_index.md

[grafanabot]

./tools/diff_coverage.sh ../loki-main/test_results.txt test_results.txt ingester,distributor,querier,querier/queryrange,iter,storage,chunkenc,logql,loki

Change in test coverage per package. Green indicates 0 or positive change, red indicates that test coverage for a package fell.

+           ingester	0%
-        distributor	-0.3%
+            querier	0%
+ querier/queryrange	0%
+               iter	0%
+            storage	0%
+           chunkenc	0%
+              logql	0%
+               loki	0%

[grafanabot]

./tools/diff_coverage.sh ../loki-main/test_results.txt test_results.txt ingester,distributor,querier,querier/queryrange,iter,storage,chunkenc,logql,loki

Change in test coverage per package. Green indicates 0 or positive change, red indicates that test coverage for a package fell.

+           ingester	0.1%
+        distributor	0.3%
+            querier	0%
+ querier/queryrange	0%
+               iter	0%
+            storage	0%
+           chunkenc	0%
+              logql	0%
-               loki	-0.7%

[grafanabot]

./tools/diff_coverage.sh ../loki-main/test_results.txt test_results.txt ingester,distributor,querier,querier/queryrange,iter,storage,chunkenc,logql,loki

Change in test coverage per package. Green indicates 0 or positive change, red indicates that test coverage for a package fell.

+           ingester	0%
+        distributor	0%
+            querier	0%
+ querier/queryrange	0%
+               iter	0%
+            storage	0%
+           chunkenc	0%
+              logql	0%
+               loki	0%

[dannykopping]

Thanks for the great contribution @taharah!
Let's wait for @KMiller-Grafana to approve the docs & merge

[KMiller-Grafana]

Docs in this PR look good to me.

[kavirajk]

Thanks @taharah 🎉

[taharah]

Just wanted to add: We deployed this into our internal environment and were able to use remote write with sigv4 authentication now 🎉