I’m trying to post three strings to a API/form. The webservice is called Nginx Proxy Manager if you are familiar. It don’t really have API docs but it uses openapi 3.1.0. I’m trying to post to this section:

   "/nginx/certificates/{certID}/upload": {
  "post": {
    "operationId": "uploadCertificate",
    "summary": "Uploads a custom Certificate",
    "tags": [
      "Certificates"
    ],
    "security": [
      {
        "BearerAuth": [
          "certificates"
        ]
      }
    ],
    "parameters": [
      {
        "in": "path",
        "name": "certID",
        "schema": {
          "type": "integer",
          "minimum": 1
        },
        "required": true,
        "example": 1
      }
    ],
    "requestBody": {
      "description": "Certificate Files",
      "required": true,
      "content": {
        "multipart/form-data": {
          "schema": {
            "type": "object",
            "additionalProperties": false,
            "required": [
              "certificate",
              "certificate_key"
            ],
            "properties": {
              "certificate": {
                "type": "string"
              },
              "certificate_key": {
                "type": "string"
              },
              "intermediate_certificate": {
                "type": "string"
              }
            }
          }
        }
      }
    },
    "responses": {
      "200": {
        "description": "200 response",
        "content": {
          "application/json": {
            "examples": {
              "default": {
                "value": {
                  "certificate": "-----BEGIN CERTIFICATE-----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n-----END CERTIFICATE-----n",
                  "certificate_key": "-----BEGIN PRIVATE KEY-----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n-----END PRIVATE KEY-----n"
                }
              }
            },
            "schema": {
              "type": "object",
              "additionalProperties": false,
              "required": [
                "certificate",
                "certificate_key"
              ],
              "properties": {
                "certificate": {
                  "type": "string",
                  "minLength": 1
                },
                "certificate_key": {
                  "type": "string",
                  "minLength": 1
                },
                "intermediate_certificate": {
                  "type": "string",
                  "minLength": 1
                }
              }
            }
          }
        }
      }
    }
  }
},

This is what I currently have. I have tried a number of other things, this just seems the most correct to save space:

url = "https://api.example.com/api/nginx/certificates/1/upload"

# This header has been working in other calls.
headers = {
  "Authorization": f"Bearer " + api_key
}

# public, private, and chain are all strings
# I've tried tuples with  None and actual text like "chain.pem"
# I've tried a straight dict without the tuple
files = {
  "certificate": (None, public),
  "certificate_key": (None, private),
  "intermediate_certificate": (None, chain)
}

response = requests.post(url, headers=headers, files=files)
print(print(json.dumps(response.json(), indent=2)))

{
  "error": "No files were uploaded"
}