As of ITPART-1180, the clientId associated to a given Azure subscription is available in the /partnerEntitlements response (for most azure subscriptions). Note: the clientId is not always available from the IT Partner Entitlement endpoint; contracts created prior to implementation of ITPART-1180 do not have the clientId recorded.

When available, swatch should use this attribute to determine which client credentials should be used to submit usage; otherwise we should try all configured client credentials.

Implementation hint: AzureMarketplaceService.sendUsageEventToAzureMarketplace should consider the clientId value from AzureUsageContext if available.

Done:

• When a contract is synced from the IT Partner gateway the value of clientId is stored as another field in the `;`-delimited billingProviderId.
• Preserve current behavior of trying all the credentials/regions as a fallback because not all contracts are populated with this information. However, we should only log an error if we are completely unable to send the data. i.e. a retry to a different endpoint/credential combination is not an error.   
• AzureUsageContext is updated to provide the value of clientId when it is present in billingProviderId
• When swatch-producer-azure looks up azure usage context and the context includes a clientId value, it should immediately use the azure client configured with the value, and not loop through any other clientId's client instances.
• Ephemeral test using wiremock to validate behavior
• Validate that if a matching credential is not found that appropriate errors are logged. 
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