Invoke timer triggered function by HTTP

I am trying to invoke my timer triggered function by HTTP for testing purposes. I can see that the portal website has a 'Run' button that firstly
retrieves an access token from https://myfunctionappname.scm.azurewebsites.net/api/functions/admin/token and then posts to https://myfunctionappname.azurewebsites.net/admin/functions/myfunctionname using the bearer token containing:
```
"iss": "https://myfunctionappname.scm.azurewebsites.net",
"aud": "https://myfunctionappname.azurewebsites.net/azurefunctions"
```
This returns an HTTP 202 and the function is executed.

I want to perform the same invocation using an automated process without using the portal or my personal azure credentials.
Is it possible to acquire an access token using the deployment credentials or some other method that will allow me to successfully post to the function endpoint?

#### Investigative information

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- Timestamp:
- Function App version (1.0 or 2.0-beta):
- Function App name:
- Function name(s) (as appropriate):
- Invocation ID:
- Region:

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#### Expected behavior

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#### Actual behavior

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#### Known workarounds

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#### Related information