Add support for feature flags

[tevoinea]

Summary of the Pull Request

What is this about?

Adds a new App Configuration resource to the onefuzz deploy.

Info on Pull Request

What does this include?

• Deploy new App Config resource
• Wire up the azure functions to allow using it
• Demo 1 case where it can be used

Validation Steps Performed

How does someone test & validate?

• Ran deploy locally
• Enabled feature flag in azure
• Validated it was enabled
• Disabled feature flag in azure
• Validated it was disabled

Ran check-pr

[stishkin]

Use managed identity instead of connection strings

App Configuration Data Reader which has GUID: 516239f1-63e1-4d78-a4de-a74fb236a071

[stishkin]

resource func 'Microsoft.Web/sites@2021-03-01' existing = {
name:
}
var readerRoleId = '516239f1-63e1-4d78-a4de-a74fb236a071'

resource assignReaderRole 'Microsoft.Authorization/roleAssignments@2022-04-01' = {
name: guid('${func.identity.principalId}-role-assignment-reader')
scope: featureFlags
properties: {
principalId: func.identity.principalId
roleDefinitionId: subscriptionResourceId('Microsoft.Authorization/roleDefinitions', readerRoleId)
}
}

[stishkin]

Deploying new azure resource just to store one value.... seems like too much ?
Are there any other configuration options we can move there as well ?

[codecov-commenter]

Codecov Report

Merging #2620 (e0bfb20) into main (af806a3) will decrease coverage by 0.00%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main    #2620      +/-   ##
==========================================
- Coverage   29.29%   29.28%   -0.01%     
==========================================
  Files         289      289              
  Lines       35755    35765      +10     
==========================================
  Hits        10474    10474              
- Misses      25281    25291      +10     

Impacted Files	Coverage Δ
...piService/ApiService/Functions/AgentCanSchedule.cs	0.00% <ø> (ø)
src/ApiService/ApiService/ServiceConfiguration.cs	0.00% <0.00%> (ø)
...ApiService/ApiService/onefuzzlib/OnefuzzContext.cs	0.00% <0.00%> (ø)
...vice/onefuzzlib/notifications/NotificationsBase.cs	0.00% <0.00%> (ø)

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[tevoinea]

Deploying new azure resource just to store one value.... seems like too much ? Are there any other configuration options we can move there as well ?

So far, I only added the one value to demonstrate how it would be used. This should be the way we do feature management going forward and also in a follow up PR I'm going to add the node dismissal strategy