Currently the user agent header value was created for each TokenDelegatingHandler and NordigenHttpClient.
By creating the header value once, both the execution time and allocated memory for GetRequiredService<INordigenClient>() was reduced.
Original:
| Mean | Error | StdDev | Gen 0 | Gen 1 | Allocated |
|--------- |---------:|---------:|-------:|-------:|----------:|
| 33.16 us | 0.102 us | 0.090 us | 5.3101 | 0.0916 | 44 KB |
After caching:
| Mean | Error | StdDev | Gen 0 | Gen 1 | Allocated |
|--------- |---------:|---------:|-------:|-------:|----------:|
| 26.02 us | 0.091 us | 0.086 us | 4.8218 | 0.0000 | 39 KB |